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FRANKLIN INSTITUTE LIBRARY 


PHILADELPHIA 


Class... 7.. Book..26.6. Accession ZA2 3F 


The book may be borrowed for 
a period of two weeks and re- 
newed only for an additional 
period of two weeks. 
LIBRARIAN. 














=a) t 











FACTORY PRACTICE 


IN 


MANUFACTURE 


OF 


~AZO DYES 


BY 


“W. B 'OBRIEN,: BEB. 13 ae: 
Chemist for the Flash Chemical Company 


Formerly wit ' the 45 tasselli: Chém: ‘ca! Company’ aud? the 
Synfeur Scientific Labovatorfes « *° 


EASTON, PA. 
THE CHEMICAL PUBLISHING COMPANY 
1924 
LONDON, ENGLAND: TOKYO, JAPAN: 
WILLIAMS & NORGATE ' MARUZEN COMPANY. LTD. 


14 HENRIETTA STREET, COVENT GARDEN, W. C. 11-16 NIHONBASH!I TORI-SANCHOME. 


ereerce 


PRON 


ce 


Canoe 


cence 





COPYRIGHT 1924, BY EDWaRD HAR 


o 


faeooenr 
€ 


PREFACE 


The purpose of this volume is to afford basis for a view point 
on azo dye manufacturing, in so far as actual factory procedure 
is concerned, for the general chemist and for those who look 
forward to the dye industry as a possible field for their pro- 
fessional activity. Informative discussion upon the manipula- 
tion and working conditions in the dye factory is not easily avail- 
able to the student. 


For presenting the elements essential to standardized produc- 
tion of azo dyes, the simplest members of that class are to be 
herein discussed, covering chiefly the mono azo group, by out- 
lining in detail specific methods for preparation of individual 
dyes with explanation of technical principles involved. In deal- 
ing with the subject of factory practice some attention must be 
given to necessary theoretical and research matters, but it is not 
intended in this volume to present the more abstract chemistry 
of the azo dyes as aclass. A factory process is merely a routine 
based upon theoretical and experimental considerations. The 
soundness of chemistry indispensable in theoretical and research 
work must be inherent in factory processes, but, apart from 
chemistry, economy in regard to labor and materials and con- 
formation to the limitations of the short working day becomes 
of paramount importance. A lay belief somewhat generally ac- 
cepted attributes an indefinable, mysterious elusiveness to the 
work of dyestuff production. Such belief, while serious enough 
in the stubbornness with which it persists, is in no way justified. 
Similarly to other large industries, success in dyestuff manu- 
facturing depends upon capital, organization and hard work. 
The advantage possessed, elsewhere than in America, due to 
earlier participation in the industry, has been largely compensated 
by economic and circumstantial factors affecting the industry 
here. 

It is hoped that the student of the subject will realize that 
alternative methods of procedure are always possible and that 
statement of fixed methods may serve only as a starting point 
for an understanding or improvement. Undoubtedly more numer- 


1 FES 4- 


1V PREFACE 


ous recipes than given herein would be acceptable, but in the 
opinion of technologists well versed in the subject, recipes are 
of value only when accompanied by explanation of the principles 
involved, and the principles which apply to mono azo dye pro- 
duction need only stricter observation for application to produc- 
tion of other, more complicated, azo dyes. 

The author is indebted to Mr. John Eliot Foster of Boston for 
his cordial help in preparing the illustrations, and to Dr. E.. von 
Salis of Albany, N. Y., for his valued direction in the production 
of dyestuffs. 


Boston, Mass., April, 1924. 


CONTENTS 


CHAPTER 1 


Te Pe a aN tae! eee ac Ne eg ad oe a be I 


Importance of the azo dyes as_a class. Chemical theory and 
nomenclature of the dyes. Outline of the factory routine 
of manufacturing. 


CLAP ER old 


Buripincs, MAjorR EQUIPMENT, OPERATION, MATERIALS ............-- 14 
Scale of operations. Buildings for the making, drying, milling 


and standardizing processes. Tubs, filters, blow-cases, stor- 
age tanks, mills, mixers, general equipment. Operation, 
maintenance, chemical materials used. 


CHAPTER, Il 


Pe Me trea OM CPP ANILINE | 7.0. 0502s cc cccewed ences Waters a ase tees 46 
Manufacture of Orange G. ; 


CHAPTER IV 


Fovye ParrAnen FROM DIAZOTIZED ANILINE $i0%...0. coeces cescdvenars 56 


Amino Naphthol Red G, Fast Acid Fuchsine B, Croceine Orange, 
Chromotrope 2B, Chrysoidine Y, Sudan I. 


CHAPTER V 
-DIAzoTIzATION oF THE HoMOLOGUES OF ANILINE ........0eeeeeceeee 73 
Manufacture of Ponceau 2R, Sudan II, Brilliant Orange O. 
CHAPTER VI 
ATO ZATION OF THE NITRO -ANILINES sos e00ccccndscedenc cas nescees 81 
Alizarine Yellow R, Paranitraniline Red, Alizarine Yellow GG. 
CHAPTER VII 


DIAZOTIZATION OF THE SULFONATED ANILINES .......ccescccceccceves 93 
Chrome Yellow AS, AM, Orange J, I], III, 1V, Metanile Yellow. 


Vi CONTENTS 
PAGE 
CHAPTER VIII 


DIAZOTIZATION OF ACETYL PARA PHENYLENE DIAMINE AND AN- 
TEHRANILIC ACID. cscs o55.c d5.0's)ele dua bap toticlc eee akc tn aa ahi tina 117 


Amino Naphthol Red B, Azo Coralline, Acid Anthracene Red B. 


CHAPTER IX 


Mono Azo Dyes FROM OrtTHO AMINO PHENOL DERIVATIVES ......... 129 
Chrome Brown R, Peri Wool Black, Palatine Chrome Violet. 


CHAPTER X 


Mono Azo Dyrs FRoM ALPHA NAPHTHYLAMINE AND NAPHTHIONIC 
ACID Lecce ened ecracb elated cu palace e8c cy 00 Nkiehee prea t= ia 137 


Fast Red B, Fast Brown N, Fast Red A, Azo Rubin. 


CHAPTER XI 
Mono Azo Dyks From AMINO NAPHTHOL SULFoNIC AcIDs .......... 149 
Salicine Black U, Sulfon Acid Blue R. 
CHAPTER XII 
TETRAZOTIZATION OF BENZIDINE <0. ..052¢¢> os ue sie ess ee eee 157 


Diamond Flavine G, Chrysamine G, Diamine Fast Red C. 


CHAPTER XIII 


RELATION OF THE CHEMIST TO THE INDUSTRY. EXPERIMENTAL WorRK 
AND SMALL SCAL® PRODUCTION |.....¢0e.uce bee ue ee 166 


LIST OF PLATES 


PAGE 

ATS foe gwd de SRA PRs Kuiek SL eRe ig & rad eV bk ale Mew ca eeee 15 
Cross section, making building. 

eee Sc ia ao 3c ona s bpd 6 6 a9 ode tcele sf Mane wale ee oe Be oe 24 
Longitudinal section, making building 

oe Sag a aaiy ble pics ¢c.s civ cies be wae cb ein he We sebues 29 
Plan, first floor, making building. 

SE a tee eos hal Sicrs ie @ as sc «ue vi ab aie *saaieud eahho.b eiaice 6 ve wis 30 
Plan, second and third floors. 

ee eA a) 4 0ha's w FEM POR OES bared ae dele Petal he ah aed eee 35 
Plan and elevation, drying department 

Pete ee ng aioe Sa cig disvos ese vrsvvavenscuscesget vec euve 38 
Plan and elevation, milling department. 

RE ee hogs gels enn-ace a SiG biate.y «'s s.g/aa vivings o MalaRi + 6.4.0 ole we 47 


Table of dimensions and content of cylindrical tubs. 


eer aE PR ET, Oi. Sale a cate el ola ds Se or Lea dew a pps eee coh 169 


Plan and elevation, experimental plant. 


FIGURES 


PAGE 
Cylindrical tub: .o0s.0c0 set oa aa nei eve oak ee 17 
Tub with slanting sides ...:45.2..%. [00 ales nen 17 
Tub with blade agitator, overhead suspension ............. 18 
Tub with propeller agitator. ...0 o. 0.» +/s00% 10 selene 18 
Agitator with bearing om tub floor .....4.),\).aee eee eee 19 
Gate type agitator ..« 05 ck bees us «ose aiie cle ee 19 
Bib cock outlet: (00084 62. cee Ale oe ete cree eee 20 
Straight type’ outlet. yo. 0200 fe. 0) a ee 21 
Location of outlets in tubs’ i..c, opacity een 21 
Special. manner of installing outlet; ...: J). ae Renee 22 
Top and sectional. views of filter tub 3. /i.2 2 yee eee 26 
Detail of filter tub fittings eievawcaw es vee sai) tne ln 27 
Sketch of frame and plate 2.2.3... .2.0 us = pee 28 
Arrangement of tubs, blow-cases and their corresponding 
filter -Pr@SS€S ....46se0rioee gas: ope scp ale cient an 3I 
Front view of drying ovens (2.2/2.7) vss ss scene 34 
Vitriol tanks ....5.caccnenvscescce ae Ue eu e's oan ne 40 


CHAPTER«I 
INTRODUCTION 


Of the dyestuffs that originate in coal tar products, the 
“Azo” dyes form a highly interesting class, including in number 
more than 60 per cent of the total dyes manufactured in the 
United States.? | 


The chemical name “azo” finds use with manufacturers rather 
than with distributors and consumers. In a discussion of their 
manufacture the dyes of this class can be identified only by use 
of the term, although the finished azo dyestuffs are classified in 
trade circles as acid, basic, mordant and direct dyes. Such com- 
mercial classifications relate somewhat to the chemical compo- 
sition of individual dyes, but do not constitute exact chemical 
classification of the dyes nor give indication as to the methods 
employed in their manufacture, and are based mostly upon the 
manner in which a dye is applied to a fabric or other materials. 
The commercial classifications include other dyes with the azo 
and do not differentiate between the simple dyes and the blends, 
or mixtures of several dyes that are marketed. 


From a chemical standpoint the azo class of dye is well de- 
fined, and once the chemical composition of a dye has been de- 
termined there is seldom any doubt as to whether or not it be- 
longs in the azo class. The molecular structure of all of its 
members has a dominating point of similarity due to the presence 
of the “azo” chromophore, a characteristic grouping of nitrogen 
atoms, represented by the symbols —N = N—, or —N,—. 
Further, dyes of this class are all prepared according to a 


1In the year of 1920, eighteen classes of dyes were manufactured in the United 
States, with total production of 88,263,736 pounds, valued at $95,613,749. Of the 
240 individual dyes which made up the classes 148 were azo, totaling 36,897,003 
pounds, value $46,984,135. The remaining 92 dyes were divided among seventeen 
classes, of which the most important numerically was the triphenyl methane class, 
with zo members and total production of 2,482,169 pounds, value $10,130,336. Of 
synthetic indigo, 18,178,231 pounds were produced, value $13,497,981. The sulfur 
dyes amounted to 20,034,500 pounds, value $6,936,703. The average price per pound 
was for azo dyes, $1.27; for triphenyl methane, $4.08; for synthetic indigo, $0.74; 
sulfur dyes, $0.25. The figures relate to actual production in the United States. 
During 1920, only 3,402,582 pounds of dyes were imported, value $5,763,437, of which 
Germany supplied 51 per cent, Switzerland 34 per cent, England 6 per cent, and 
other countries 9 per cent. (U. S. Census of Dyes and Coal Tar Chemicals for 1920). 


2 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


general method which varies but slightly in detail for each 
member. 

The raw materials consumed in manufacturing azo dyes are in 
themselves highly developed products of the chemical industry, 
known as “intermediates.” They include amines and phenols of 
the aromatic series of organic chemistry, and derivatives such as 
the chlorinated, nitrated, and sulfonated, amines and phenols. It 
is extremely practical to combine the manufacture of the inter- 
mediates with that of the dyes, into one organization, but the 
discussions of methods and equipment for manufacturing the 
products of each of these two industries must be taken up sepa- 
rately. In this volume it is assumed that the raw materials, or 
“intermediates,” are furnished, and in a condition suitable for 
their use in the production of dyes. 

Manufacture of an azo dye begins with the preparation of a 
diazonium salt, ordinarily referred to as a “diazo.” The follow- 
ing structural formulas represent typical diazonium salts: 


N,Cl N,Cl 


a Ge 
WA Nae 


Benzene diazonium chloride Naphthalene diazonium chloride 
or Diazo benzene chloride or Diazo naphthalene chloride 


Preparation of such diazos is effected in the factory by the action 
of nitrite of soda on the water solution or suspension of an 
aromatic amine, usually in the presence of an excess of a mineral 
acid. The amino group is converted into a diazonium group, the 
reaction being called “diazotization,” and for aniline, is repre- 
sented as follows: 


NH, N,Cl 


fay Mou 
| | + HNO,+ HCl = | | + 20H,O 
wy Ny 
Aniline Diazo 

benzene chloride 


INTRODUCTION 3 


The diazos as a class react quantitatively in water solution with 
certain amines and phenols, and derivatives, a reaction termed 
“coupling” taking place. A compound reacting thus with a diazo 
is termed a “component.” Coupling produces new compounds, 
containing the groups of atoms that were formerly diazo and 
component, united by the azo group, —N = N—, as shown in 
the equation for the coupling of diazo benzene chloride and 
beta naphthol : 


N,Cl N ==== 

Bee NOX 
ae | 

we SLE LASS ETON AG 


Diazo Beta 
benzene chloride naphthol Sudan I 


The product of the above reaction, Sudan I, is a typical azo dye, 
with a chromogen containing the azo group as a chromophore 
and the hydroxyl group as an auxochrome. Dyes of greater 
complexity can also be prepared, containing more than one azo 
group and therefore of greater dyeing power. The number of 
auxochromes in an azo dye can be varied by selection of the 
diazos and components. Only primary amines can be diazotized, 
but the composition of materials adapted for use as components 
varies considerably, including primary, secondary and tertiary 
amino compounds, and phenolic compounds, used in the forms of 
the acid and basic salts. 


As a rule, the diazonium salts do not possess much stability 
and so must be used immediately or at least soon after prepara- 
tion. Directions for their preparation and use in the factory 
should include specifications as to the material and construction 
of the containing vessel and the character of the mechanical 
agitation applied. The solubility of the amine and concentration 
of its solution or suspension, the manner of introducing nitrite 
of soda, the duration of the diazotization, the temperature 
throughout and the final volume, must be considered for secur- 
ing the diazo. The diazo results and is used in solution or in a 
suspension; if sufficiently insoluble, it may be filtered for use. 


4 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Difficulties of preparing components for coupling vary with 
the solubility of their salts in water. It is generally desirable to 
effect solution in the smallest volume attainable. If heating is 
necessary to bring the component into solution, the temperature 
must be brought down again before coupling, with of course due 
consideration for the form in which the component reprecipitates. 
A component can be used in solution or in a suspension. 


Coupling action between diazos and components is promoted 
by a favorable condition of solution, which may be alkaline, acid 
or neutral, depending on the nature of the component. The alka- 
line condition is regarded as that produced by soda ash; the acid 
condition that from muriatic or sulfuric acids; the neutral con- 
dition that from acetate of soda or bicarbonate of soda. In gen- . 
eral, phenols and their sulfonic acids couple well in alkaline solu- 
tion, amines in acid solution and the amino sulfonic acids best in 
neutral solution. To effect coupling in either the alkaline or 
neutral conditions, the prepared diazo is added to the solution 
of the component containing soda ash or acetate of soda. For 
coupling in acid condition, the component is added to the solution 
of the diazo; ordinarily sufficient acid will be present to maintain 
this condition without further addition of acid. Special cases 
occur where the diazo is prepared in solution with, and in the 
presence of, the component; in these cases the components are 
amines and coupling goes on in acid condition. 


In calculating the amounts of diazo and component to be pre- 
pared it is customary to take a slight excess of one of the two, 
depending upon the influence which the unused excess will have 
upon the finished dye. Ideal procedure would require that ex- 
actly equivalent amounts of each reacting material be taken but 
absolute exactness in control is unattainable in practice and the 
employment of an excess of one insures complete utilization of 
the other with advantage to the results. 


The time required for the completion of a coupling reaction 
in the factory depends much upon the efficiency of the contact 


INTRODUCTION 5 


obtained between the diazo and component. In case both are 
completely soluble, reaction may be completed immediately after 
mixing, or at the most within a few hours. In the cases of 
slightly soluble diazos and components, used in suspension, as 
much as forty-eight hours’ agitation of their mixture may be 
necessary to completely utilize the one present in lesser amount. 
Efficient agitation and a fine state of division in the reacting ma- 
terials promotes the contact and is necessary for completing the 
coupling reaction. The less soluble diazos are to be had in a 
finely divided condition as result of the method of their prepa- 
ration, but a process should include directions for producing this 
state for slightly soluble components used in suspension. The 
volume or concentration of the coupling mixture influences the 
progress of the reaction differently for individual cases. Some 
azo dyes on formation precipitate immediately in a thick slimy 
state of particles which hinder contact between unreacted por- 
tions of the diazo and component and completion of such coup- 
ling is favored by efficient agitation rather than by concentration, 
but in cases where the resulting dye is very soluble, or else pre- 
cipitates in a crystalline form, concentration is advantageous. 

While diazotization and coupling are chemical reactions which 
ordinarily may proceed smoothly in the manner indicated by 
their written equations, secondary reactions must nevertheless 
be anticipated. In the course of its formation a diazo may react 
with a portion of the undiazotized amine, to form a compound 
having the nature of a dye but undesirable. In the lesser stable 
diazos partial decomposition may occur to form phenolic com- 
pounds which will later couple with the diazo in alkaline solu- 
tion; the yield, as well as the purity of the dye, is thereby 
lessened. ‘The necessity for use of pure intermediates is em- 
phasized by a consideration of the influence of secondary re- 
actions upon the finished dye; small amounts of alien color 
formed may alter the shade sufficiently to destroy the value of 
the product. 

Completion of the coupling reaction is recognized by testing 
a portion of the mixture for presence of the material taken in 


6 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


excess and absence of the other. In a practicable industrial 
method the dye is out of solution after completion of the coup- 
ling, and it is generally filtered in an alkaline condition, after 
addition of common salt, up to 15 per cent of the total weight 
of the charge, to the solution to insure complete precipitation. 
The mechanical work of filtering, drying and pulverizing the 
dye comprises a large part of the total work of the manufacture. 


In so far as purely speculative organic chemistry ts concerned, 
the number of possible azo dyes is almost unlimited. Commer- 
cial enterprise uses only the simpler compounds, including the 
mono azo, disazo, trisazo and tetrakisazo dyes. The Greek pre- 
fixes refer to the number of azo groups contained in a molecule of 
the dye compound; a mono azo dye is the result of simple union 
between a diazo and a component, and contains but one azo 
group, —N = N— or —N,—. Orange II is a mono azo dye, 
as shown by its structural formula: | 


N SS et N 
a . ee Bice: 
ye eI 
SO,Na 
Orange II 


Of these dyes the disazo type finds use in the industry to a 
greater extent than the other three types, and is further sub- 
divided according to the manner of formation, into, (a), pri- 
mary and secondary disazo dyes, and (b), disazo dyes from 
diamines. The disazo dyes are prepared from the mono azo 
dyes by employment of reactions entirely similar to those used 
to form the mono azo. It is sometimes the case that a com- 
ponent has the power of coupling with two molecules of diazo; 
resorcin is such a component. When coupled with one molecule 
of a diazo, resorcin gives a mono azo dye in which the com- 
bined resorcin nucleus may again react as a component and 


INTRODUCTION Fi 


couple with a second molecule of a diazo. The compound formed 
by the second diazo contains two azo groups in the molecule and 
is termed a disazo dye. The two molecules of diazo used may 
be of the same composition, in which case symmetrical dyes are 
formed, or of different composition, giving rise to “mixed” or 
unsymmetrical dyes. In either case a primary disazo dye re- 
sults from this manner of formation. The first coupling takes 
place much more readily than does the second and it is neces- 
sary to couple the lesser stable of two diazos in a first operation, 
forming the mono azo dye and to then introduce the second and 
more stable diazo. A longer duration of the coupling period, 
and adjustment of the conditions of temperature and alkalinity, 
is required to bring the slower second coupling to completion. 
The case of Resorcin Brown is illustrative of this type of dye; 
the slightly stable diazo from meta xylidine is coupled with 
resorcin and the mono azo dye resulting is then coupled with a 
molecule of the diazo from sulfanilic acid: 


OH 


Meee Ace.) 

/NCH, GH. (0) 1) 

oa le | AGE 

Ry NH, 
3 CH, ; 

Xylene Resorcin OH 
diazonium N,——7 ee NN oe 

chloride Je os NEC ET nt a 
| Ue Ps eh bs Oem te AGH. 

Bak ee LON Ge N 


ke CH, | 


3 
Benzene N 


diazo sulfonate 


~$O,Na 
Resorcin Brown 


Secondary disazo dyes differ from the primary only in man- 
ner of formation; no radical dissimilarity appears in the compo- 
2 


8 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


sition of the finished dyes; a mono azo dye obtained by coupling 
a diazo with an amine or amino sulfonic acid will contain a free 
amino group as auxochrome; the amino group may be diazotized 
in the conventional manner and the secondary diazo resulting is 
usually stable, coupling readily with components to form second- 
ary disazo dyes. Sulfon Cyanine Blue G is an example of the 


type: 


N,-—O NH, Nee Ng NE, diazotize 
TAN Ni NTS AN 
aR et his | | = aN a with 

Diazo benzene a-Naphthylamine 
m-Sulfone | 

MAN ONE es 
a NC DN NO eee Ci PNAC 

: ys J Ns0.Na oe Cone 

3 3 
CJ soNa ee 
Sulfon Cyanine Blue G Phenyl peri salt 


In the case of dyes of this type there is no great difficulty in 
promoting the second coupling. 

Primary diamines of the aromatic series give rise to a class 
of disazo dyes. In some diamines the two amino groups can be 
“tetrazotized,” or diazotized simultaneously, yielding a “tetrazo” 
analogous to the diazo. Extensive use is made of meta phenylene 
diamine, benzidine, and their derivatives, in producing disazo 
dyes by means of tetrazotization. In the preparation of Bismarck 
Brown the two amino groups of meta phenylene diamine are 
tetrazotized in one operation but in the case of this dye the 
component is also meta phenylene diamine, and tetrazotization 
is performed in the presence of the component; coupling with 
two molecules of the component follows immediately to form 
the disazo dye, it not being possible to limit the reaction of either 


INTRODUCTION 9 


of the diazonium groups and control the introduction of the 
component: 


NH, 
% a + 2NaNO, + 4 HCl => 
oH, 


Meta phenylene diamine 


N,Cl NH, 
| eu are 
\/N,CI \/NH, 


NS 
cue er DNH, HCl 


Bismarck Brown 


This behavior, of simultaneously tetrazotizing and coupling, 
is peculiar to the meta diamines and constitutes a special case. 
Ortho and para diamines cannot be tetrazotized and indirect 
methods must be used to obtain the disazo dyes which theoretic- 
ally correspond to such diamines. Dyes derived from ortho dia- 
mines have no commercial importance but this cannot be said of 
the dyes derived from para diamines, especially para phenylene 
diamine. Two methods are used for preparing disazo dyes from 
such diamines. The first method starts with a mono acetyl dia- 
mine, the free amino group of which is diazotized and coupling 
made with a component to form a mono azo dye. The acetyl 
amino group is then split by a process of hydrolysis and the amino 
group set free for diazotization and a subsequent coupling. 
Violet Black B is a disazo dye prepared in such manner: 


IO FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


NWHCOCH = ONECOCEH. NHCOCH, 
C Kn ah A/S om (1) 
was ii oe A Nhe 

NH, N,Cl O,H N=N/SV\/S\ 

Acetyl para —- Diazo N- wr Acid meray | 
phenylene ee ee 
diamine SO,Na 
NH, N,Cl 
(1), +H SOpte 7 Ne ae aN 
| (IT) 
OH ed 
Baia AaN meme 
Bs akeae’ Waa 
; SO, 
NH, N=WN Be. 
LES 7 mr 
CET) Gch ae cee | | | C 
Ona a 
a-Naphthyl pee OH 
amine N= Bae. 
SO,Na 


Violet Blank B 


The second method uses a nitro amine, which is diazotized and 
coupled with a component. The nitro group in the resulting 
mono azo dye is then reduced to an amino group, which is diazo- 
tized and the second coupling made to form the disazo dye. The 
above two methods introduce more highly involved chemical 
operation than is usually met with in the course of azo dye manu- 
facturing. Added complications in operation need not necessarily 
be accompanied by a decline in the yield but, increased cost in 
equipment and operation can be sufficiently heavy to eliminate 
possible products from a field of competitive production. 


INTRODUCTION II 


Diamines of the biphenyl series, benzidine and its homologues 
and derivatives, can be directly tetrazotized; the tetrazo formed 
couples with components in a manner which can be controlled 
for each diazonium group to the extent that one diazonium group 
may be coupled with a molecule of a component while the other 
diazonium group is held unchanged, for subsequent coupling 
with a molecule of a second component: 


NH, N,Cl OH MAN oes 
ee OO ON NL) 
i L | | is) Ler, —COONa 
ae xX + Salicylic ye 
Pe: a acid | (I) 
ee Og MA 
NH, N,Cl N,Cl 
Benzidene ‘Tetrazo 
diphenyl 
dichloride 
OH Ne n~. OH 
Be 7S > Couns 
ee eae ee ue be 
Oe NA net 
Gamma Fhe Diamine . 
acid ied Fast Red C 
A 
Ns N OH 
ae A ~ 
cy \/80;Na 


The disazo dyes of this type are of importance from their prop- 
erty of dyeing cotton without aid of a mordant. 

Azo dyes containing three, or four, azo groups in the molecule 
are prepared by methods similar to those used in forming the 
mono azo. A simple illustration is in the case of a trisazo dye 
which can be prepared from phenol as component with three 
molecules of diazo which may be introduced in steps, forming 
a compound whose formula is: 


12 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


OH 
X—N=N /\ N=N—Z 

Leu 

Peed oa 
N xX, Y and Z = aromatic radicals. 
| 
N 
Y 


Of the trisazo dyes which have commercial importance, Benzo 
Brown 3-GO may be mentioned. In preparing this dye, two 
mono azo dyes are first formed separately, one by coupling meta 
phenylene diamine with a molecule of the diazo from sulfanilic 
acid, the other by tetrazotizing benzidine and coupling one of 
its diazonium groups with a molecule of salicylic acid as com- 
ponent; the two mono azo dyes are then mixed and the free 
diazonium group of the benzidine nucleus couples with the meta 
phenylene diamine nucleus to form the trisazo dye compound: 


NH, ap NH, N==N 
Sn pene os A a 
OOM Gl pe (I) 
ee SN Ba 
SO,H So, - SO,Na NH, 
NH, N,Cl N==N 
ine OH LX 


NH, N,Cl N,Cl 
VN oe 
ost 
(I)+(Ud1D= \/ Benzo Brown 3-GO 
yom 


INTRODUCTION 13 


Only few tetrakisazo dyes are manufactured. Compounds con- 
taining more than four azo groups are seldom commercialized. 
The difficulty of preparation increases with the number of azo 
groups, due to the difficulty of bringing the slower higher coup- 
lings to completion and to the accumulative influence of second- 
ary reactions. The yield of the finished dye should increase with 
the number of azo groups proportionately to the molecular 
weight, making it possible to overcome the cost of an expensive 
intermediate by coupling it with several of low price. 

The manufacture of azo dyes from intermediates may be out- 
lined as follows: 

I. Coupling. 


vue 


Preparation of the diazo, including (1), all work 
necessary in procuring, weighing, acidifying, dis- 
solving and icing the amine; (2), preparation of 
the nitrite of soda solution and addition of it to 
the amine. 

Preparation of the component, including procuring, 
weighing, dissolving in acid or alkali, and icing. 
Combining, or mixing the diazo and component, 
and observance of the time for completion of the 
reaction, also neutralization and salting of the 
finished charge. 


II. Filtration. 


By 


Conveying the charge to suction tubs or to blow- 
cases for filtration. 


B. Filtration, washing, removal of the cake. 
C. Finishing some dyes as paste. 
III. Drying. 
A. Entering the paste in proper type of oven and tray. 


B. Duration of the drying and treatment of the dye. 
IV. Milling. 

A. Grinding. 

B. Standardization, including dye laboratory tests and 


addition of the proper reduction materials. 


CHAPTER II 
BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 


In the manufacture of azo dyes the unit quantity of the pro- 
duction is the batch or charge. For practical work the batches 
prepared should be of a size sufficient to yield from 500 to I,000 
pounds of dye, selling strength, in a single charge. On such a 
scale the production can be of sufficient volume to carry the 
manufacturing expense, while the size of the batches is not too 
great for good control and completion within twenty-four hours. 


The molecule charge, based on a molecule of the diazo in 
pounds, such as would be obtained from 93 pounds of aniline, 
in the case of diazo benzene, is conveniently of the size de- 
sired, yielding in many cases about 1,000 pounds of dye when 
the product has been reduced to selling strength. The molecule 
charge is made the basis for methods of procedure to be taken 
up later. The coupling equipment should be constructed with 
capacity to carry such charges and have ample room for excess. 
In some cases it is necessary to conduct larger charges, of from 
two to five molecules in size, to maintain the volume of the pro- 
duction when the molecular weight of the dye compound is low, 
or when the selling strength of the product is highly concentrated 
and little or no reduction can be allowed; in such cases the 
equipment described will serve. 


For the work of coupling and filtering, an entire building 
should be allotted, drying and milling to be conducted in a sepa- 
rate building. In practice such a scheme for operation is fol- 
lowed rather than one which combines the manufacturing pro- 
cess entirely within one building. Plates A, B and C show sec- 
tional views of a building designed for the ‘“‘making” or coupling 
and filtering of azo dyes, with equipment for conducting eight 
charges per diem. Points in which the difficulties of the making 
process can be reduced include the handling of raw materials, 
providing ready access to the coupling outfits for introduction 
of raw materials and the transfer of charges from one section 


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L/12 LAS /2 








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MENGES IE 











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s 








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AYFTIWVI-Y 





16 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


to the next. Plans? of the three floors or working levels are 
shown in Plates C-1, C-2 and C-3; a raised center portion of 
each floor, shown in Plate A, allows access to the top line of 
coupling tubs located on the lower side portions of the floors; on 
the third floor the sides are left partially open, for transmission 
of power, and for light. The coupling units are housed within 
a main section of the building, the first floor being extended with 
a shed roofing on each side to house the filtration equipment. 
Elevator space is made near one end, where raw materials are 
received. Storage bins for salt and ice flank the elevator on the 
first floor, the corresponding space on the second floor being 
allotted to laboratories for the chemical control, and on the third 
floor to space for location of a small plant for experimentation 
with new methods. The coupling tubs on the lower side floors 
are placed closely along the raised center floors, and raw ma- 
terials, handled on the center floor, can be entered in the tubs 
without the use of chutes or hoists. It is desirable to minimize 
the installation of fixed chutes as far as possible; much incon- 
venience attends their use. In general construction the building 
should be of a steel frame with brick or tile walls, the floors to 
be of reinforced concrete, supported by steel girders and up- 
rights. The ventilation afforded in the building designed will 
ordinarily be adequate for the needs in azo work but ample 
window space must be allowed for light. Provision should be 
made, in the form of openings, pits and tunnels, for the pipe 
lines, water, sewer, steam, vacuum and compressed air, with 
easy access for inspection and repair as alterations and repairs 
figure prominently through a period of dyestuff manufacturing. 
The coupling reactions are conducted in wooden tubs fitted 
with connections for water and direct steam, and mechanically 
driven wooden agitators. The materials for diazo and component 
are dissolved in tubs on the upper levels and the solutions de- 
livered progressively to lower levels during operation. A charge 
2The plans and designs shown do not refer specifically to those of any plant in 
use at the present time, as far as the author knows, nor are they intended for use 
other than to illustrate the practical features of the specialized work of azo dye manu- 
facturing. Buildings in use by manufacturers result from their special needs, for com- 


bining the manufacture of intermediates and dyes or to adapt buildings constructed 
for other purposes, to the manufacture of dyes. 


BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 17 


ordinarily flows by gravity but when filtering with pressure the 
charge flows into a steel blow-case located in a pit sunk in the 
first floor and is then forced up into the filter press by means of 
compressed air. For vacuum filtration, filter tubs are placed on 
the raised portion of the first floor. Batches filtered by vacuum 
are to be coupled and finished on the second floor and run by 
gravity to the filter tubs. Greater rapidity may be obtained by 
using pressure filtration; the steel blow-cases used for alkaline or 
neutral batches must be specially equipped with an interior lining 
of lead or acid resistant brick for acid charges filtered by pres- 
sure. 

The wooden tubs for this work are built from 3-inch stock, 
of cypress, redwood or white pine. Sizes of tubs vary with 
their purpose, ranging from about 200 gallons upwards to 3,000 
gallons in capacity. The manner of arrangement of tubs is 
illustrated in Plate F. Two types of tubs are in use, the first 





AANA 
MTT 
WT 


eee 








CKLIVORICAL TUB- STRAIGHT SOLS TUB WITH SLAINTING HIDES 

Fig. 1 Fig. 2 
having vertically straight sides, giving the same diameter at top 
and bottom, bound with round iron hoops drawn tight with 
malleable iron draw lugs; the second type has a slanting side 
giving less diameter at the top, bound with flat iron hoops se- 
cured in place to prevent slipping unwards. Tubs are cylindrical 
in shape excepting some of the larger which have an oblong con- 
struction. 


18 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


For rapid calculation of the exact volume occupied by solutions 
at various depths, required intermittently in azo work, the first 
type is more desirable; exact measurement of volumes is essen- 
tial for the control. Greater durability and length of service is 
claimed for the second type. Tubs should be set in place with 
the bottom at a slight pitch towards the outlet in order that the 
contents may be emptied completely without much rinsing and 
washing. 

Mechanically-driven agitators are employed in all tubs except 
those used for dissolving nitrite of soda. The single-blade type 


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SSS SSS SS SSS 
1 LT Ti 


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Rea 


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y 
Z 
Z 
Z 
Z 
Y 
Z 
Z 
Z 
Yj 
Y) 
Z 
Y 
Z 
Z 
Z 
Y 
4 


a 
RSS 
108 





BLADE AGITATOR WIT WERHEAD PROPELLER AGITATOR 
SUSPENYS/O/Y 
Fig. 3 Fig. 4 


of agitator shown in Fig. 3 is used and should swing to clear 
the bottom by not above 3 inches. The propeller type of agi- 
tator, Fig. 4, is installed for processes requiring very rapid agita- 
tion and may clear the bottom by 6 or 8 inches. Suspension of 
the agitator should be from bearings at two points in the upper 
section of the agitator shaft, as indicated in the figures. 


BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS I9 


The type of agitator resting on a metallic stud in the bottom 
of the tub is not suitable for azo work as the stud, even if of 
brass, is eaten out periodically by muriatic acid in conjunction 
with nitrous acid, causing delay for repairs and mishap to the 
charge under preparation; the stud also forms a center around 
which mud, soda ash and debris will cake. Wooden pegs for 
securing the agitator blade to the bottom of the shaft are more 
suitable than brass bolts although in this case the matter of re- 
newing brass bolts is much simpler than the removal of an acid- 
eaten stud. Fig. 5 illustrates the type of agitator to which ob- 
jection is made. The gate type of agitator, Fig. 6, is likewise 
unsatisfactory from its undue splashing of material during agita- 
tion, but has some use for slow agitation of heavy mixtures. 





oe 
i 
1 





SS SSSSSSS 





= 
ESSSSSSSSSSSSSSSSST'ASSSSSSSS SSS 
= 





A es a we SMS Le il SS) 





BLADE AGITATOR BEARING | CATE T¥PE AGITATOR 
OMY TUB SLOOR 
Fig. 5 Fig. 6 


It is desirable to have the blade of an agitator swing within 
3 inches of the tub floor for agitation of small initial and final 
volumes; thus, in a tub 8 feet in diameter the smallest amount 
of water that could be agitated would be 784 pints. If the agi- 
tator cleared the bottom by 5 inches, the corresponding amount 
would be 1,307 pints, the difference becoming more noticeable in 


20 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


larger tubs. For pastes or mixtures running out of tubs it is 
desirable to agitate as long as possible to prevent settling. 


In many instances the methods for diazotization and coupling - 
call for strong agitation. Agitation to comply with this specifi- 
cation varies in rapidity depending on the diameter of the tub 
and the density of the mixture to be worked. A tub 6 feet in 
diameter could not have a blade agitator running at much over 
forty revolutions per minute, as when filled to any depth prac¢ti- 
cal for working, the material would flow over during agitation. 
In a tub of large diameter a blade agitator running slowly will 
effect as strong agitation as a more rapid agitator in a smaller 
tub; in a tub 8 feet in diameter, agitation at twenty-four revo- 
lutions per minute, would suffice for diazotization of a moder- 
ately thick “H” acid paste where forty revolutions per minute 
would be required for the same material in a tub 6 feet in diam- 
eter, the difference being due to the relative sweep of the blades. 
Studs secured to the sides of the tub are of little advantage, work- 
ing best below the surface. The propeller types of agitator, hav- 


BIB COCK TX¥PF OUTLET -LARTHENWARE 
Fig. 7 


ing shorter arms or blades, has little effect on heavy pastes but 
is used at high speed to produce a smooth rotation of solutions 
or thin suspensions. In tubs used for dissolving nitrite of soda, 
large paddles worked by hand are used for agitation as the quan- 
tity of solution is small; care must be taken to completely dis- 
solve and use all of the nitrite. 

Outlets for discharging the contents of tubs are of earthen- 
ware or hard rubber, especially in cases where acid is to be used. 
The hard rubber material is affected by heat and should not be 
used where temperatures of over 50° C. are attained. as is the 
case when dissolving alpha naphthylamine hydrochloride. 
Earthen-ware cocks are not entirely satisfactory because of their 


BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 21 


brittleness; the straightway type is more suitable than the bib- 
cock, cakes of paste, bits of wood and other debris which fre- 
quently obstructs the channels of cocks being more easily re- 
moved with a stiff wire. 


cont Cum 


STRAIGHT WAY TYPE OUTLET-LAPTHEN WARE 
Fig. 8 


Outlets may be advantageously set in the tubs in two posi- 
tions, the first by screwing the outlet through the tub bottom at 
a point adjoining the side wall, as in Fig. 9, the second by screw- 
ing the outlet through the side wall on a line with the bottom, 
as in Fig. 10. The first setting is the usual one, with the second 
as alternative when the tub sits too close to the floor to allow 
access to a bottom outlet. 
















SS 





TASS 



























Wy 
Hy 7UB 7UB 
et INTERIOR | WYTERIOR 
| Wh ree 
Wye Wee Caesar. 
| We jo 








LOCATIONS OF OUFLETS 
MWY TOBS 
Fig. 9 Fig. 10 


22 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Such outlets are simple to install, require no metal retainers, 
and have no angles in the channels. A system of installation 
shown in Fig. 11, is one that should not be employed; a block 
attached to the bottom of the tub by means of bolts or pegs, has 
a channel bored down from the tub and through from the out- 
side, meeting at right angles; with a bib-cock for outlet two angles 
result in the channel to augment difficulty from an obstructed 
channel. 







ed 





8 Ty 
waerat (El) 8 2a a, 


40; ini ALLL LSS) Pa 


C422 
a? 18 BRO 


NI 






aN 





SPECIAL IIAIVIYER OF LIYSTALLIVYC OUTLET 
Fig. 11 


Attention should be given to providing outlets of sufficiently 
large size, it being a common error to install a size considerably 
too small. A suitable size is that of a cock with a channel of 
1¥4 inches diameter, so that from an ordinary tub 1,000 gallons 
may be discharged within thirty minutes. 


Transfer of contents from one tub to a lower is made through 
a stout rubber hose 2%4 to 3 inches inside measurement, fitted 
over the tapered end of the outlet and run to the lower floor 
through the openings between floors. Such equipment is cheap 
and easy of replacement; the charges flow from the tubs with no 
loss from leaks or retention in angles such as can happen with 


BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 23 


a fixed chute; one hose may be used to discharge alternately to 
any of several tubs below, where a fixed chute can do for only 
one connection and is costly to install if made compact and last- 
ing. The construction of the building, (Plate A), allows a man 
to reach the outlet of a tub on the next floor, with a short step 
up, and regulate the flow of a charge without the necessity of 
ascending to the upper floor to halt the charge at a critical 
moment. 


Solutions from the nitrite of soda tubs are run down through 
a i-inch, or larger, iron pipe connected in the bottom of the 
nitrite tub and running to a diazotization tub below. A valve is 
placed in the nitrite pipe close to the outlet from the tub; a 
second valve is placed at the discharging end of the pipe so that 
once the flow of nitrite solution has been started, it may be 
regulated at the diazotization tub. 


Main pipe lines for water and steam are located directly under 
the raised portion of the third floor; water pipes to the tubs 
should be of 2-inch size and the open ends should not run far 
down into the tubs, to avoid contact with acid solutions. For 
heating alkaline or neutral charges a 11%4-inch steam pipe, secured 
to the inside wall of the tub and running down to the bottom 
will give the desired temperatures by passing live steam directly 
into the solution. The iron steam pipes should be removable 
and have an elbow attached at the bottom to avoid shooting 
steam directly at the tub floor. For heating water to obtain a 
concentrated solution, the nitrite dissolving tubs are also equipped 
with iron steam pipes. For heating acid solutions, a 4-inch by 
4-inch wooden pipe with an 1% bore is used to replace the 
iron steam pipe; the bottom of the wooden steam pipe should 
be plugged and exit for the steam made through %-inch holes 
bored in the sides of the pipe. Wooden pipes used for heating 
may split after a period and need to be replaced but in general 
they give satisfactory service. The wooden pipes are also in- 
stalled to conduct nitrite of soda or other solutions to the bottom 
of an acid charge, instead of using metal or composition pipes. 
All pipes used within the tubs should have flanking side boards 
as protection during agitation. 

3 


24 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 










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BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 25 


A useful installation is that of a small water faucet at each 
tub, with a short length of hose attached, for rinsing down tubs 
after the contents have been discharged and for washing out 
tubs preparatory to use; in the latter case the washings may be 
run to the sewer through a 3-inch hose. Sewer holes on each 
floor should be not more than 15 feet apart and be protected by 
wooden gratings. For a supply of hot water for washing filter 
clothes and filter press plates a spare tub, 6 feet in diameter by 4 
feet deep, may be located on the first floor in the shed extension, 
and connected with water and steam. 


A completed charge contains the dye as a precipitated solid 
suspended in many volumes of the mother liquor. Separation is . 
made by a filtration of either the vacuum or the pressure type. 
Vacuum or suction filtration is done in low wide tubs built 
from a stock similar to that of the coupling tubs. A standard 
size for filter tubs is 7 feet in diameter by 3 feet in depth. A 
set of planks, drilled with perforations, forms a partition or 
false bottom at 12 inches from the top, Fig. 12. The perfora- 
tions are Y%4 inch in diameter and spaced 2 inches apart. The 
surface of the planks is scored with a network of grooves con- 
necting the perforations, Fig. 13. 

To prepare a filter, a layer of burlap cloth is laid on the false 
bottom and a layer of heavy canvas superimposed, the two 
layers then drawn tight and secured in place by a flat stave nailed 
to the side of the tub, Fig. 14. The chamber under the false 
bottom is connected to a vacuum line by a pipe fitted into the 
side of the tub closely under the false bottom and provided with 
a valve and vacuum gauge. A bib-cock outlet for discharging the 
filtrate is fitted into the side, close to the true bottom, and a vent 
hole for the chamber is bored in the side and closed with a 
wooden spigot. 


A filter should be thoroughly wetted and soaked before using 
for the first time, and may then serve for a number of filtra- 
tions. ‘To make a filtration, the outlets of the vacuum chamber 
are left open and as much of the charge as possible is run onto 
the bed of the filter; the outlet and vent holes are then closed 
tightly and the vacuum line opened slowly. As filtration pro- 


26 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


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TSS 


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leg SSDP ISIS Sa eeT SIR SARs: AAAAAAAAARARAARRAR SEER QUERESERERESURGRIESS SSS 


SAMA. 
WAST SS. 





SECTIONYAL VIEW OF FILTER TUB 
Figs. 12 and 13 


ceeds, the liquor draws off from the solid in the bed, leaving a 
cake containing much mother liquor, much of which can be 
pressed out further with a hand float, this treatment being also 
necessary for maintaining the vacuum, by closing cracks and 
openings that form in the cake. As soon as the vacuum chamber 
under the partition becomes filled with liquor, the vacuum line 


BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 27 


is closed and the chamber emptied, to prevent the liquor from 
getting into the vacuum line. The cake may be washed with 
water from a shower arranged over the tub, if the process re- 
quires it, and the vacuum applied again; the cake is finally re- 
moved, using a wooden shovel so as not to cut the cloth. Acid 
charges are usually filtered by suction as there is no contact with 
metal in such a system; if much acid material is to be filtered 










SSS: 








Seeevess 
Ws ose 


Ss 


INNES 


ss 


SS 







Ss 


SS 
RS 
















SS 


S55 





NSN 
SS 





Ss 





WSs 


ES 






G 





>, 


DETAIL OF FILTER TUB FITTUVES 
Fig. 14 


a wool cloth should be substituted for the cotton; the cloth is 
to be inspected for holes before filtration. A state of vacuum 
up to 25 inches is indispensable for good work in the factory, 
for rapid filtration and a cake low in moisture. Individual dyes 
vary greatly but the speed of filtration can be judged from a 
test made in the laboratory by filtering a sample on a Buchner 
funnel. Suction filtration has the disadvantage that the coupling 
tub must serve as a reservoir for the charge during the hours 
of filtration, preventing use of the tub for preparing the next 
charge, as only a portion of a charge may be filtered at a time; 
very little gain can be made by forcing the filtration. 

Pressure filtration of azo dyes utilizes a series of wooden 
frames and plates held together in a horizontal screw press. 
A standard size for such frames and plates is 24 inches square 
by 2 inches thick. The press consists of two parallel steel bars 


28 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


30 inches apart, terminating at ends in fixed sections of steel, 
one of which acts as a base where the charge is fed into the 
press; at the opposite end a movable steel section, or head, rests 
between the bars by means of elbows and is moved by a screw 
held in the cross piece which unites the bars. The plates and 
frames also rest between the bars on elbows. ‘The plates are 
solid and have their two surfaces gouged with a set of close 
vertically parallel grooves which terminate at the top and bottom 
in a larger, horizontal groove which is connected to a channel 
bored through the plate to form a passageway to the exterior. 





FRAME PLATE 
Fig. 15 


The plates are each covered with a layer of tightly stretched 
canves. On one side of the plates and frames a 2-inch hole is 
bored; when the press is made up and tightened, a plate alter- 
nating with a frame, the concentric 2-inch holes on the side form 
a channel through which the charge from the blow-case is forced ; 
the hollow part of the frames is in connection with this channel 
by means of a slot cut so that material is delivered to the hollow 
center of the frame where the solid remains while the liquor 
passes on through the canvas of the adjacent plate and follows 
the grooves and channel out through a spigot, for removal. The 
flow of liquor from the spigots diminishes and ceases as the 
press fills. The solid cake remaining in the press contains some 
liquor and may be further pressed out by blowing air through 


BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 29 


Gi 
DIN7HD 
LSU UALIE 


thd XS 


Gi 
DT RAIO? 
WOILIE 


SOW FAWOD DLISIVOD 
Wee OOTY DSAFMOT 


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8 
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LSM HN LLE 


ME LTYS 


ol Sa Sweety 
WIT Fovsols Chey & 
OL AMALIA 


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en 2 
SSS 
= SS LE 


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IN TA/OD j— = 
WO LASS 


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IM TSOP 
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ASHUVLIE 


FLTAINOD 
2007, M/W 


LJ 0HS 
eOLATTIF 


[ penerc a 


MEG FH 





30 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


the press, for which purpose a small channel is located in the 
upper part of the plates and frames, by a series of concentric 
34-inch holes, connected with the air pressure line; this channel 
is also connected to a water line for washing a cake in the press 
or for wetting up a press to keep it tight when not in use for a 
period. To remove or “dump” the cake the air and feed valves 
are shut, the press unscrewed, the cake removed from the frames 
by hand with an iron scraper and the press closed up for further 
use. The cake falls into a trough below the press and is shoveled 
into barrels for delivery to the drying room. 


OVAZOTISATIONY TUBS 
LOWERED SIDE FLOOR, COMCRET 





PLATE C-2 PLATE C-3 


212. FLOOR BRD. FLOOR 


Plate A shows the location of the filter presses in the side ex- 
tension of the first floor. The blow-cases are located in a pit 
between the presses and the main building. A blow-case is 
essentially a closed cylindrical vessel made from %-inch boiler 
steel, equipped with an agitator and connected to the air pres- 
sure line. The dimensions of a blow-case with capacity for hold- 


BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 31 


ing about 1,500 gallons would be a diameter of 6 feet with a 
nominal height of 6 feet augmented by a convex top and bottom 
to a total height of 9 feet. To operate, an escape valve is opened 
and the agitator started; the outlet valve in the connection from 
the making tub to the blow-case is then opened and the charge 
transferred from the making tub to the blow-case; all valves 
are then closed and the air pressure applied, from 25 to 50 
pounds pressure per square inch being required; when suf- 
ficient pressure is indicated, the outlet is opened in the pipe 
leading from the bottom center of the blow-case to the filter press, 
gradually until liquor begins to run from the press spigots, when 
the full stream may be allowed to flow into the press. 
Filtration of the dye is a slow procedure and frequently holds 
back production; for this reason it is sometimes necessary to 
make use of several presses for one charge; a series of connec- 
tions made between the different units, as shown in Fig. 16, per- 


mits use of several filters for one tub. 
= COUFLIIVG 





FILTER PRESSES 









i COUPLIYG 
CASE TUB 


Fig. 16 


Upon completion of a filtration, a small quantity of water may 
be run from the making tub through the blow-case and press to 
prevent caking the dye in connecting pipes. The wash out valve 
in the connection between the making tub and the blow-case in 


32 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Plate F may be used for emptying tubs without the necessity of 
passing the liquid through the blow-case. 


In a dye factory steam is ordinarily supplied from a central 
power plant of the factory; vacuum and compressed air may be 
supplied from a central plant or furnished by pumps located in 
the azo building. For forcing the charge through a filter press, 
individual pumps may replace the blow-cases, but are not en- 
tirely satisfactory, partly from the service which a blow-case 
gives as reservoir to hold the finished charge, leaving the making 
tub free for the next charge. 


Power for agitation is furnished from within; two 10 horse- 
power electric motors, one for each side of the building serve for 
agitation of both tubs and blow-cases. The motors can be located 
on the first floor, with belt drive to the main power shaft on that 
level, which in turn drives the main shaft for the two upper 
levels; each tub has individual belt drive from the main shaft and 
is furnished with fast and loose pulley. A gallery should be 
constructed within reach of each main shaft to allow access to 
the driving pulleys for repairs to belts and changing of pulleys, 
and for use when oiling the shaft bearings; the location of such 
galleries is indicated in Plate A. Power for other equipment, 
such as mixing apparatus, ice crusher, elevator and various small 
pumps, is furnished by individual motors. Mixing equipment is 
required for reducing pastes to uniformity; dyes sold as pastes 
are taken directly from the filter to the mixer and either diluted 
or strengthened in tinctorial power. This procedure is necessary, 
as the wet filter cake of each charge varies in content of the dye, 
however closely controlled the process of making may have been, 
and the marketed product must be of a uniformly standard 
strength. The mixer should be located in close vicinity to a 
filter to avoid carrying the paste; after mixing the paste is 
dumped into barrels for weighing and shipment. Intermediates 
received in the form of pastes, for use in making the dye, must 
be put through a mixer before a sample of the intermediate can 
be taken for analysis, as the paste dries unevenly in barrels and 
a true sample can be obtained only after mixing thoroughly; the 
mixer for this work should be located on the working floor of 


BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 33 


the second level where such pastes find most of their use; to 
fill the mixer the barrels of paste received are taken to the third 
floor and the contents shoveled into the mixer on the floor below. 
Intermediates are used in paste form to eliminate the cost of 
the drying and grinding operations necessary to produce a 
powder; a paste is more easily dissolved than the corresponding 
powder, and the advantages attending the use of pastes over- 
come minor difficulties in their handling. 

A platform scale may be built into the first floor near the 
elevator for weighing stores received, especially for large pack- 
ages such as drums and barrels. Small movable scales with 
capacities up to 500 pounds are located on the three working 
floors for weighing out portions of the charges. 


During full production, over 50 tons of salt may be con- 
sumed in one month; the storage bin should be large enough to 
hold an adequate supply. Ice is to be received daily from an 
outside storage; artificial ice, containing no debris, is preferable 
to natural ice; the storage for ice within the making building 
should be large enough to accommodate a minimum amount of 
fifteen tons per diem. For conveying salt and ice to the tubs, 
carts may be constructed with capacities for holding accurately 
500 pounds of each of these materials, eliminating the need for 
weighing each load; attention should be given to good construc- 
tion in the carts so that one man may handle a load without 
assistance. 


DRYING, MILLING AND. STANDARDIZING 


The most of the azo dyes are marketed in a powder form, 
hence the wet product of the making building must be dried and 
pulverized. Drying of any batch of dye consumes more time 
than does the work of coupling and filtering; a charge may be 
completely coupled in twenty-four hours and filtered within an- 
other twenty-four hours for each set of tubs and filters, but dry- 
ing for the same charge will require from four to eight days. 
Adequacy of facilities for drying permits of speed in production. 


34 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


The mechanical character of the work of drying necessitates 
very little chemical control other than that to indicate the high- 
est temperature permissible for the various dyes. Drying is done 
in stoves or ovens containing the wet paste on pans or trays. 
Space for such ovens is usually allowed on the ground floor of 
a building. Plate D shows an arrangement of twelve ovens to 
be used in connection with the scale of operations described for 











a 





| 

















ieee ss 
fSeremESTh 
pa 











| 
| 


| 
| 


| 
Hi 
|| 




















| 
| 









































FLA Ht HL 


a 
Pof___ sb 


FROWT VIEW OF DRYUYC OVENS 


Fig. 17 


the making of the dye. The construction of ovens suitable for 
this work is not restricted to any special style; generally they 
are box-shaped with brick or steel walls, the front side con- 
sisting mainly of steel doors, the other sides closed. The dimen- 
sions of the ovens indicated in Plate D would be 16 feet long 
by 6 feet wide and 7 feet high, each oven being divided into 
three compartments of about 4 feet width and each compart- 
ment divided into two sections, the sections to have shelves 3 
inches apart on centers, to hold twenty-five pans in tiers; such 
an oven would accommodate one hundred and fifty pans. Pans 
for this style oven are 20 inches wide by 40 inches long and 1% 
inches in depth, of a steel of No. 20 gauge thickness. Heating 
is accomplished by means of a current of air which passes over 
coils of steam pipes contained in a special compartment at one 
end of the oven; a fan at an aperture in the opposite end causing 
the circulation; baffle walls constructed within the oven route the 
air current throughout to give contact to all the pans. In place 


BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 35 








Nena eee A ee 


FLATE 2 





of fixed section, use may be made of movable trucks for holding 
the pans. Such trucks may be withdrawn from the stove and 
loaded with pans or withdrawn to allow the pans to cool before 
handling, thus minimizing the time during which the doors must 
be kept open. Hydrochloride salts of basic azo dyes, such as 
Chrysoidine and Bismark Brown, cannot be dried on metal pans, 
wooden trays being substituted for these. 


36 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


The wet paste received from the making building contains from 
50 per cent to 60 per cent of moisture on the average; some pastes 
run as high as 70 per cent in moisture and others as low as 30 
per cent, varying with the character of the filtration. The 
temperatures maintained in the ovens vary from 50° C., up to 
go° C., depending upon the susceptibility of the dye to decom- 
position from prolonged heating; some few dyes may not be 
dried as high as 50° C. Individual dyes vary in their behavior 
on drying; a Metanile Yellow paste containing much moisture 
will dissolve in its moisture if entered directly in a hot stove; 
this does no damage of itself but loss and nuisance can result 
from warped or unlevel pans and it is necessary to dry at a low 
temperature until most of the moisture has been driven off, when 
the full heat of the oven is necessary to obtain a product dry 
enough to grind. An Azo Rubin may be entered to a hot stove 
directly but has the peculiarity of forming rocky hard lumps 
which are difficult to break up and retard the drying. 

Treatment of the dye is simple in description. The paste is 
laid out in pans to a depth of about % inch; and entered in the 
oven; after several days’ drying the pans are withdrawn and the 
friable cake broken up and turned over by hand, this treatment 
being repeated several times during the drying; the extent of the 
drying can be observed by crumbling a specimen in the hands. 
The dried product is put into barrels for delivery to the milling 
department. 


The general run of azo colors is not considered explosive, 
more dangerous members of the class having become less used, 
but some azo dyes are known to ignite and burn with a smoldering 
flame during drying or milling; the Alizarine Yellows, R and GG, 
are often mixed with 3 per cent ammonium sulfate before enter- 
ing into the ovens, to prevent possible ignition. 

Milling procedure includes grinding of the dye to a powder 
and then mixing to uniformity after addition of salt or other 
ingredients; the same mill serves both for grinding and mixing. 
Mills of several sizes and types are in use, the principle employed 
being that of a revolving steel drum containing loose steel balls 
or other fragments of steel for abrasion and crumbling of the 


BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 37 


dye. Mills are either cylindrical or spherical in shape; a cylin- 
drical mill 4 feet long and 3 feet in diameter serving for the 
amount of dye obtained from a one-molecule charge. The ar- 
rangement of mills on a floor above the oven room is shown in 
Plate EF. Large mills, of 8 feet length and 6 feet diameter are 
located on one side of the floor, for use in mixing together of 
several charges. Mills are loaded through openings fitted with 
manhole covers; for loading the larger mills, access is obtained 
from the third floor. Several hours’ time suffices for pulver- 
izing a well dried charge in a mill revolving sixty times per 
minute but mixing may require twenty hours. 

The materials used for diluting or “reducing” the dye include 
chiefly common salt and sodium sulfate; these materials must be 
dry and finely ground. In some cases aniline salt and the cheaper 
spirit soluble gums are used for mixing with the spirit soluble 
dyes. When a batch of dye has been thoroughly pulverized, 
a sample is tested for the tinctorial value by dyeing a small 
amount of yarn or other suitable material, and comparing the 
strength and shade produced with that of an equal weight of the 
standard dye applied under identical conditions; the strength of 
the standard dye is rated at 100 and the strength of the batch is 
reported in percentage equivalents; that is, the batch is ordinarily 
stronger than the standard and is rated as 60/100, 65/100, etc., 
in reference to the number of parts which are equivalent in 
strength to 100 parts of the standard. The weight of the batch 
being known, calculation can be made to determine the amount 
of salt to be mixed; the standardization is completed by gradu- 
ated addition of the salt and repeated dyeing tests. 

Common salt is mixed with direct dyes and dyes which are 
to be applied in a sulfuric acid bath, including the mordant dyes 
and acid dyes; also with basic azo dyes. Sodium sulfate is 
mixed with dyes which are to be applied in a bath acidified with 
acetic acid, such as the “sulfon” colors. A dyestuff may be 
marketed in several strengths, such as the “ordinary,” and the 
“concentrated,” with greater, or less, reduction in the milling. 
Certain of the “highly concentrated” wares consist of unreduced 
dye, the manufacture being directed. with a view to obtaining as 


—_ 


BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 39 


pure a product as possible, with less regard for yield and cost 
in the production. Reduction of dyes is not considered adulter- 
ation or falsification but is an operation necessary for obtaining 
a consistently standard product, due to the fact that no two 
batches run to similar strengths as first prepared. Discrepancy 
in the strengths of dyes marketed for the same brand by differ- 
ent manufacturers comes from a difference in standards adopted, 
but the products of one factory can be expected to be in accord- 
ance with the standards announced by that factory. There is 
nothing, however, to prevent a purchaser from remilling and 
further reducing the dye for resale; the appearance of dye does 
not indicate the general extent to which reduction has been made, 
and only a laboratory test of each package can show the actual 
strength of the dye. 


MATERIALS 


Chemicals used in the manufacture of azo dyes are of two 
kinds, industrial chemicals and coal tar intermediates. The in- 
dustrial chemicals, inorganic bases, acids and salts, are of con- 
siderable bulk and their handling requires regard for convenience 
and saving of labor as well as for economy of materials. 


Fused caustic soda, the industrial sodium hydroxide, is 
marketed in thin sheet iron drums holding about 700 pounds of 
a grade containing 76 per cent of sodium oxide. For its use, 
cylindrical iron dissolving kettles 5 feet in diameter by 4 feet 
deep will hold the solution of 40° Bé. density made from 700 
pounds of caustic soda; the proportions for such a solution are 
roughly two pints of water to one pound of caustic. A dissolv- 
ing kettle should have water connection and an iron steam pipe 
running down to the bottom to heat and agitate when dissolv- 
ing. The main dissolving kettle may be located on the third floor 
and connected by a 2-inch iron pipe with iron plug cock valve, 
to a similar kettle on the second floor; the solution made on the 
third floor can be run to storage and use on the second floor 

4 


40 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


while another solution is being made up and allowed to cool; a 
dissolving kettle must contain no liquid when the solid caustic 
is being thrown in. 

To make up a solution for factory use, a drum of the caustic 
soda is pounded on the seams with a sledge hammer, breaking 
up the caustic within and splitting the cover open. This requires 
about twenty minutes’ pounding; the workmen must wear goggles 







SUPPLY PIPE 
FRO PAI STORAGE 






STORAGE TANYA 
FOR VITRIOL 









CAUSTIC SODA | 






G 
= eerecaerprrerces— 


OURE (Clise; 








STORAGE 


Fig. 18 Fig. 19 


when handling the solid caustic. The caustic is shoveled into 
the kettle and 1,000 pints of water run in, a mark being kept in 
the side to indicate the proper depth, about 17 inches from the 
bottom; steam is passed slowly through the mixture for an hour 
to agitate and the batch then allowed to stand until next day, 
occasionally stirring with an iron bar. The solution made is run 
down to the storage kettle on the second floor, the gravity taken 
at room temperature and dilution made to 40° Be. density for 
use; the connecting pipe between the kettles should be washed 
down to prevent caking. A 40° Bé. solution contains 35 per cent 


BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 4I 


of sodium hydroxide; 115 pounds of such solution contains a 
pound molecule or 40 pounds of too per cent sodium hydrox- 
ide and calculation of the proportion to be used in a charge is 
made on the basis of this figure. One drum of 700 pounds per 
diem should be sufficient for the needs of this factory during 
full production. For conveying caustic liquor from the storage 
kettle to the tubs where used, it is ladled out into an iron weigh- 
ing bucket large enough to hold a molecular weight, and trans- 
ferred to the tubs; a set of two-handled 25-gallon iron buckets 
may be used for this work; one man with a flat cart can 
handle 115 pounds of caustic liquor unassisted and avoid the 
splashing that accompanies the use of small pails. A set of 
similar-sized wooden buckets or half barrels can serve in the 
same way for handling pastes and salts. 

Soda ash is handled in bags of 200 and 300 pounds content, 
the grade used is a practically pure anhydrous sodium carbonate 
powder containing 58 per cent of sodium oxide; on long standing 
in damp weather the soda ash takes up moisture from the air 
and lowers in relative strength. Soda ash is mainly used for 
neutralizing the acid of the diazo in coupling; the molecule for 
factory use is taken as 106 pounds, the soda ash being neutralized 
only to the bicarbonate stage to avoid frothing in the charge. 
Large amounts of soda ash should be entered slowly into a charge 
as the powder hydrates immediately in cold water and may form 
a rocky mass in the tub, stopping agitation and very difficult to 
break up. 

Acetate of soda is used in some couplings instead of soda ash 
to neutralize the mineral acid. The technical crystalline material 
has three molecules of water present and 138 pounds is taken 
as a molecule. The material is very soluble and gives no trouble 
in use. 

Bicarbonate of soda is used for neutralization in a few special 
cases; the technical grade may be regarded as pure for factory 
use. 

Muriatic acid, the hydrochloric acid of industry, comes on 
the market in standard strengths of 28.14 per cent, 32.10 per cent 
and 35.39 per cent, or respectively of 18°, 20° and 22° Bé. density. 


A2 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


The 20° Bé. acid is used for azo work as it is ordinarily the 
cheapest, price figured on the net content of hydrogen chloride; 
115 pounds of this acid is taken as a pound molecule for factory 
work. The manner in which muriatic acid is received at any one 
plant depends largely upon local circumstances; if tank cars are 
received, the acid is drawn off into standard carboys of uniformly 
115 pounds net content. To avoid nuisance and injury from 
splashing, the carboys should be plugged with large well-fitting 
wooden stoppers; for short periods of handling these are better 
than the ordinary glass stoppers used. 

The average diazotization requires 300 pounds of muriatic 
acid; two carboys may be dumped directly into the tub, by in- 
verting the carboy and resting on the side of the tub with the 
help of a supporting bar laid across the tub; the remaining por- 
tion, or 70 pounds, is drawn from a carboy by means of a hard 
rubber band siphon, into an earthen-ware vessel and weighed. 
A carboy can be carried by two men using long sticks caught 
under the cleats nailed on the sides of carboy cases for that pur- 
pose; a better method is to use a flat cart capable of carrying 
several carboys. Carrying carboys on stevedore trucks result in 
damage to carboys and accidents; the dumping of a carboy on a 
block of wood to pour out the acid is undesirable for the same 
reasons. 

Sulfuric acid is used to some extent in azo work. A 66° Bé. 
oil of vitriol with 100 per cent content of hydrogen sulfate is the 
form sulfuric acid employed; 50 pounds of the vitriol is taken 
as one molecule for factory use. A heavy iron tank of one ton 
capacity may be used for storage for use in the azo building; the 
vitriol is drawn through an iron plug cock outlet, into iron 
buckets similar to those used for carrying caustic soda solution; 
the storage tank is connected by pipe line to the main vitriol tank 
outside the making building and supplied by means of air pres- 
sure. 

For most purposes sulfuric acid may be replaced by muriatic 
acid; vitriol added to solutions creates much heat, requiring 
extra loads of ice to bring the temperature down sufficiently, off- 


BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 43 


setting economy derived from the difference in price of the two 
acids. 


In the case of persons splashed with vitriol, the vitriol should 
first be wiped off as completely as possible with cotton waste or 
cloth and the person then deluged with water from a hose or 
shower, but to use water without removing the vitriol only adds 
to the injury. 

Commercial 56 per cent acetic acid is used for some work and 
is received and stored in wooden barrels; the amounts required 
are drawn with a hand siphon pump into wooden buckets.’ The 
commercial material varies somewhat in its content of acetic 
acid and should be analyzed before use. 


Technical nitrite of soda, containing about 95 per cent of 
sodium nitrite is usually marketed in barrels of about 600 pounds 
content. The molecular weight is taken as 72 for factory pur- 
poses. For diazotization of a molecule of an amine, 72 pounds of 
the technical nitrite of soda is weighed into a bucket and trans- 
ferred to a nitrite dissolving tub, such as shown in Plate F, con- 
taining 200 pints of hot water or 300 pints of cold water, and the 
bucket carefully rinsed into the dissolving tub; solution is easily 
made in this proportion by stirring with a hand paddle; the solu- 
tion usually contains bits of wood and paper from the nitrite 
barrels and the tub outlet should be screened to prevent clogging. 


The coal tar intermediates for use as raw materials are of 
different forms, liquids, solids and pastes; they are smaller in 
bulk than the industrial chemicals and relatively more valuable. 
Liquid intermediates are of two kinds; those which are naturally 
liquid, and those which are water solutions. Aniline or “aniline 
oil,” dimethyl aniline, the toluidines and xylidines, are handled 
in steel drums holding about 700 pounds of each; the drums are 
stored in the vicinity of the tubs where used and the amounts 
required, such as 93 pounds of aniline oil, drawn with a hand 
siphon pump into a weighing bucket for transfer to the tub. 
Water solutions of the sodium salts of acid intermediates, such 


44 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


as metanilic acid or the phenyl peri naphthylamine sulfonic acid, 
are used in factories where the intermediate has been manu- 
factured on the grounds and can be delivered to the azo build- 
ing while yet in solution, to avoid the expense of isolating the in- 
termediate. For concentrated solutions, large drums holding 
about 1,000 pounds may be used to transport the liquor, as in 
the case of metanilic acid, where 975 pounds of a 20 per cent 
solution of sodium metanilate would contain one molecule, or 
195 pounds of the metanilate; to use the solution, a rotary hand 
pump is fitted into the bunghole and the contents pumped into 
a large weighing bucket for transfer to the tub. For solutions 
to be used in large amount, tanks may be installed in the storage 
space under the first floor, (Plate A), and filled from the inter- 
mediate factory through a pipe line or by dissolving a large 
batch of the intermediate in a tub in the azo building and running 
the solution down to storage; such storage tanks must have con- 
necting pipe lines for pumping the solution to the tub where 
used. For dilute solutions, of 3 per cent content or less, measure- 
ment is made by volume rather than by weight, filling a tub to 
a depth which corresponds to the volume required. Intermedi- 
ates very often handled in solution include meta phenylene 
diamine and acetyl para phenylene diamine, and many special 
cases; these intermediates are also handled as solids. 


Solids and pastes are transported in wooden barrels. The 
volumes occupied by intermediates in the paste or the powder 
forms are usually similar; the paste form has the disadvantage 
of extra weight for long transportation, but no dust nuisance 
accompanies its use in the factory. Some solid intermediates are 
to be had in the form of almost 100 per cent pure powders or 
crystals, such as sulfanilic, anthranilic, and salicylic acids, naph- 
thylamine, diphenylamine, and the nitro anilines, but in general 
the percentage composition of commercial intermediates varies 
with each lot produced and used; the materials used in the 
factory are seldom as pure as those met with in the laboratory, 
cost of purification on a large scale being prohibitive. Certain 
impurities, such as moisture and inorganic salts and acids, are 
not objectionable in intermediates used for azo dyes provided 


BUILDINGS, MAJOR EQUIPMENT AND OPERATION, MATERIALS 45 


the true content of the intermediate is known, but insoluble salts 
such as calcium sulfate and carbonate are undesirable, and 
especially so are the organic compounds isomeric with the inter- 
mediate or similar to it in composition, as they make exact 
analytical determination difficult and tend to produce off shade 
in the finished dye. The molecular weight of an intermediate 
_ must always be stated to give significance to the percentage con- 
tent of a commercial product; metanilic acid has a molecular 
weight of 173 but is often sold with analysis based on the con- 
tent of sodium metanilate, molecular weight of 195; free “H” 
acid has a molecular weight of 319, but the commercial product 
is usually the monosodium salt with more or less water of crystal- 
lization and the percentage may be based on several molecular 
weights. The purity of materials such as sulfanilic acid, 
diphenylamine, the nitro anilines and the simpler sulfonic acids, 
can be readily determined with the technical methods of analysis, 
either by titrating a weighed sample against standard nitrite of 
soda solution, or by coupling with a standard solution of diazo 
benzene chloride, and by the physical tests. Difficulty is met in 
cases such as a mixture of ““R” and “G” salts, where the isomeric 
impurity would not be apparent from an ordinary coupling test. 
In the case of “H” acid, two possibilities of analysis are met, 
one of titrating its amino group with nitrite of soda solution, the 
other of coupling with a diazo solution; in a chemically pure “H” 
acid the two determinations should give results agreeing within 
the limits of error allowable for analytical procedure. For a 
paste, discrepancy between these two determinations would 
actually be greater than is apparent, that is, an “H” acid which 
analyzed 40 per cent for diazo value and 39 per cent for nitrite 
value, would be 100 per cent and 97.5 per cent if reduced to 
the dry basis, with an actual difference of 2.5 per cent in the 
determinations. Intermediate should be reanalyzed before use, 
as a routine of operation. 


CHAPDERMAY 


' THE DIAZOTIZATION OF ANILINE AND MANUFACTURE 
OF ORANGE G 


In Chapter III and the subsequent chapters, methods for the 
manufacture of certain monoazo dyes are outlined. The system 
to be followed includes a standard practical method for the prepa- 
ration of each diazo, followed by directions for coupling the 
diazo with various components and treatment of the dye formed. 
Plate F illustrates the arrangement of equipment necessary for 
such industrial methods; Plate G is for assistance in calculating 
the quantities of solutions in tubs from the measurement of the 
depth. General details of operation have been taken up in Chap- 
ter II. 


Diazotization of Aniline.2— 
Aniline, C,H,N, Molecular Weight = 93. 
NH, NCI 


eee ert tS) 


Aniline Diazo benzene chloride 


Materials.— 
93 lbs. aniline = 1 mol. 
285 lbs. muriatic acid, 20° Bé. 
2,000 lbs. ice 
tub No. 6 
72 lbs. technical nitrite of soda 
300 lbs. water 
tub No. 4 


Method.—A tub 6 feet in diameter and 6 feet deep, fitted with 
agitator to turn at a speed of thirty revolutions per minute (tub 
No. 6, Plate F), is used for the diazotization. 

A nitrite of soda solution is made up in a tub 3 feet in diameter 
and 3 feet deep (tub No. 4, Plate F), by running in water to a 


8’ This preparation is to be referred to as Diazo-1 when its use is directed in the 
subsequent pages. 


NOWLVAT TF TUNOLLITS SSOP) _ ZL Vi of 





ihidds 


Viti. 





Ah 


WEEE cde 





O79 2076 e 
O79 = 07640-// PA 
O79 9 9 
~O79 O78 ¢ 
OF «OS Ev2 
-O7€ vO 23/ 
WLIAFTD = ASPLIWVWG DN 
SHIL SO SENOENGIMIG FOS 


Pe 
-LN09 WHYALIWMAS QWIGUNG 


|| To. 
i 


NOLVASTIS TK TALIINO7T 





48 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


depth of 7 inches, to give 300 pounds and dissolving 72 pounds 
of technical nitrite of soda. 

One thousand pounds of cracked ice is entered in tub No. 6; 
93 pounds of aniline is entered on top of the ice and followed 
by 285 pounds of muriatic acid (2% mols.). The mixture stiffens 
at first but begins to liquefy immediately afterwards and the 
agitator is then carefully started. An additional 1,000 pounds 
of ice is now added and the nitrite of soda solution in tub No. 4 
is started flowing down in a fine stream onto the surface of the 
agitating mixture in tub No. 6. The flow of the nitrite of soda 
solution is adjusted so as to take thirty minutes for its addition. 
The temperature must remain below 2° C., throughout the period 
of reaction, and will do so under the above conditions except 
possibly in the hot season when an extra amount of 500 pounds 
of ice may be required to cool. When all of the nitrite of soda 
solution has been added and the nitrite dissolving tub also rinsed 
down, agitation is continued for fifteen minutes, when the diazoti- 
zation can be considered complete and the solution ready for 
testing and use in a coupling. The agitation may be stopped, as 
an aid to maintaining the low temperature. 

The solution as prepared should have a volume equal to that 
of approximately 3,000 pounds of water, and should fill the 
diazotization tub to a depth of 20 inches; the temperature must 
not be allowed to exceed 5° C., before coupling. A distinctly 
mineral acid reaction should be obtained when a test is made 
with Congo Red paper, and a portion of the solution seen through 
a test-tube should be almost water white and should give the 
following reactions; a drop of the solution on starch potassium 
iodide paper should immediately show an intense blue color,* or, 
if no excess of, free nitrous acid is shown to be present by the 
above test, 10 cc. of the solution on addition of one drop of 
tenth normal nitrite of soda solution, should give the blue color- 


* Solutions containing commercial muriatic acid will gradually develop a blue color 
when tested on starch potassium iodide paper, even in the absence of free nitrous 
acid, but the effect is not pronounced, whereas that from free nitrous acid is distinct 
and immediate. 


DIAZOTIZATION OF ANILINE AND MANUFACTURE OF ORANGEG 49 


ation when tested with starch potassium iodide paper, indicating 
complete utilization of the aniline; 5 cc. of the solution treated 
in a test-tube with 2 cc. of a Io per cent solution of sodium 
acetate should not give the yellowish color of the iminoazo com- 
pound. The tests should be made immediately and the use of 
the diazo in a coupling commenced within one hour from the 
time at which the diazotization was started. 

Observance of the conditions outlined above assures a small 
volume in the diazo solution. Aniline undergoes diazotization 
at a speed proportionate to the concentration of the mineral acid 
present and unnecessary dilution is to be avoided. The small 
volume is advantageous for ease in controlling the temperature 
and obtaining a good yield of the dye to be formed in the sub- 
sequent coupling operation. Preparation of this diazo should 
never be commenced until the component has been prepared and 
held in readiness for coupling. 


ORANGE G° 


Orange G is prepared by coupling diazotized aniline with the 
2:6:8 naphthol disulfonic acid, or “G” salt, in alkaline solution. 


NasO, N,Cl 
EI) 9 ER aN 
| | be) {iat Na,CO, => 
NaSO,\/\/ oe irae 
‘*G”’ salt Diazo-1 
NaSO, N ==== 


a 
(to? EeNeHCO! NaCl 


Orange G 


Preparation of the Dye.— 
“G” Salt, C,,H,O,S,Na,, Molecular Weight = 348. 


5 Also known as Fast Light Orange, Orange 2G, Crystal Orange, Patent Orange 
and by other special names. 


50 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Materials.— 


355 lbs. ““G” salt, 100 per cent 
150 lbs. soda ash 
2,500 lbs. water 
500 lbs. ice 
tub No. 8 
I Ib. mol. Diazo-1 
tub No. 6 
1,000 lbs. salt 


Method.—A tub 9 feet in diameter and 6 feet deep, fitted with 
an agitator to turn at a speed of thirty revolutions per minute 
(tub No. 8, Plate F), is used for preparing the component and 
coupling with the diazo. 


Two thousand five hundred pounds of water is run into tub 
No. 8, filling to a depth of 8 inches, and the agitator started. A 
quantity of “G” salt, in powder or paste form, containing 355 
pounds of the 100 per cent material (1 mol. plus 2 per cent ex- 
cess), is entered and dissolved. The material should dissolve 
easily and the solution should be slightly alkaline; if there is 
difficulty in obtaining a solution, or if the reaction is acid, caustic 
soda solution should be added gradually and in small amounts 
until the reaction shown on Brilliant Yellow test paper indicates 
slight alkalinity. One hundred and fifty pounds of soda ash is 
then added and dissolved. ‘The component is now ready for 
coupling and may be allowed to agitate while Diazo-1 is being 
prepared as directed above. 

When the diazo is ready, 500 pounds of cracked ice is entered 
in tub No. 8, to bring the temperature down to 5° C.; the diazo 
solution is then run down from tub No. 6 in a moderate stream, 
the flow of the diazo solution being adjusted so as to complete 
the addition within forty-five minutes but not so fast as to cause 
excessive frothing in the coupling tub. As the diazo solution 
strikes the surface of the component, an orange red precipitate 
may be observed; most of the precipitate redissolves so that 
when the diazo has all been added and tub No. 6 rinsed down 
only a portion of the dye is out of solution. Agitation of the 


DIAZOTIZATION OF ANILINE AND MANUFACTURE OF ORANGE G 51 


charge is continued for fifteen minutes and a test then made to 
ascertain the completeness of the coupling. The laboratory test 
upon a sample portion of the charge should show the presence 
of a slight excess of “G” salt, and absence of the diazo. One 
thousand pounds of common salt is then added to the charge 
and agitation continued for one hour to dissolve the salt and pre- 
cipitate the dye. The charge is tested in the laboratory for com- 
pleteness of the precipitation and then delivered to a blow-case 
for pressure filtration. 


The volume of the finished charge should not be greater than 
that of 6,000 pounds of water, sufficient to fill the coupling tub 
to a depth of about 18 inches; the precipitated dye is crystalline 
in character and has no abnormal bulk to swell the volume. The 
reaction should be very slightly alkaline, sufficient to slowly 
redden a Brilliant Yellow test paper in a manner similar to that 
of a solution of bicarbonate of soda. The laboratory test for 
presence of “G” salt in slight excess is made by spotting out a 
drop from a sample of the charge onto a pinch of salt on a piece 
of filter paper, allowing the liquor to seep away from the spot 
of dye; a drop of freshly prepared tenth normal diazo benzene 
chloride solution is streaked along the outer rim of the seepage 
and the juncture will show a thin red line if “G” salt is pres- 
ent. The presence of uncombined diazo is shown by spotting 
a drop of the sample and treating in the same way with a freshly 
prepared 2 per cent alkaline solution of ‘“H” acid; in this case 
a violet line shown at the juncture of the seepages would be 
positive indication for the presence of free diazo. If tests for 
both diazo and component are positive, the coupling reaction is 
incomplete. ‘The extent to which the dye has been precipitated 
by salt is tested by spotting a drop of the charge on filter paper 
and observing the degree to which the seepage is colored; if 
there is only slight streaking, or “bleeding,” the salting out may 
be considered complete, but experience is necessary for properly 
judging by this test. 

Filtration of Orange G is rapid and without points of special 
difficulty; a compact, firm cake is obtained. Because of the 
small bulk of the cake obtained from a one-molecule charge it 


52 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


is best to use only ten of the frames (24 inches square) of a 
filter press, reversing the eleventh plate so as to block the feed 
to further frames. Filtration could be made by vacuum with 
equally satisfactory results, but for that purpose the diazo would 
need to be prepared on the third floor and the coupling made on 
the second floor, the finished charge being run to the suction filter 
shown on the raised center portion of the first floor (Plate F). 

Drying of this dye is comparatively rapid, only about 35 per 
cent of moisture being present in the cake; the initial tempera- 
ture used should be 60° C., and after twenty-four hours’ time 
the full heat of the oven may be allowed. 


Statement of the yield to be obtained depends upon the stand- 
ard of selling strength adopted. Considerable reduction is made 
in this dye for the market, a typical, strong selling standard be- 
ing that in which the marketed product contains one part of 
pure dye and one part of salt. The molecular weight of the dye 
compound is 452, that is, 452 pounds of pure dye constitutes the 
yield theoretically possible from a one-molecule charge; reduction 
with an equal weight of salt makes the theoretically possible 
yield of standard 904 pounds. With due regard for the purity 
of the “G” salts used and for exactness of the control in pre- 
paring the diazo, the yields to be averaged during a twelve months’ 
period of production depend upon the final volumes obtained in 
the charges and the completeness of the salting out process. 

Orange G is taken as a typical azo dye, presenting no variation 
from the general method of manufacture. It does not rank as 
one of the most important of the class; for the year of 1920, 
120,874 pounds valued at $1.22 per pound were produced in the 
United States. During the same year 11,143 pounds were im- 
ported from Germany, the figure undoubtedly relating to a very 
highly concentrated ware for purpose of competitive sale and 
minimization of tariff charges.® 

Orange G is used for dyeing wool in acid bath, dyeing easily 
and level; the shade produced has excellent fastness to light, 
steaming and ammonia when applied to either new wool or car- 


6 The figures of domestic production and import given above and later are from 
the United State Census of Dyes and Coal Tar Chemicals for 1919 and 1920. 


DIAZOTIZATION OF ANILINE AND MANUFACTURE OF ORANGEG 53 
bonized wool. Silk, weighted or unweighted, is dyed with good 
fastness to light. When mixed silk and wool is dyed the silk 


results in a lighter shade than the wool. 


PLAte G.—DIMENSIONS AND CONTENTS OF CYLINDRICAL TUBS. 








When filled to When filled to 
_ 1 inch depth— s -——1 foot depth—— 
Bottom Volume Pounds Gallons Pounds Gallons 
Diameter, area in of of of of 
inside Sq. it. ene T: water water water water 
2'0” 3.14 .262 16.3 1.96 196 23.5 
gs 3.41 284 17.7 21% 213 25.5 
2'Qh 3.69 .307 19.2 2.30 230 27.6 
aa” 3.08 331 20.7 2.48 248 29.7 
24" 4.28 350 22.2 2.67 267 32.0 
25° 4.59 .382 23.8 2.86 286 34.3 
25° 4.91 .409 25.5 3.06 306 36.7 
oa 5.24 437 27.3 3.27 327 39.2 
2'8” 5.50 465 29.1 3.48 348 41.8 
2'9” 5.04 495 30.9 3-70 370 44.4 
210" 6.30 525 32.8 3.04 304 46.1 
eit” 6.68 557 34.8 4.17 417 50.0 
3'0" 7.07 580 36.8 4.41 4AI 52.9 
3/1” 7.47 .622 38.8 4.65 465 55.9 
aia” 7.88 .656 41.0 4.91 491 58.9 
ara 8.30 691 43.2 TF 517 62.1 
a4" 8.73 fa7 45.4 5-44 545 65.3 
3/5” 9.17 .764 47.7 5.72 572 68.6 
3'6" 9.62 802 50.1 6.00 601 72.0 
aie* 10.08 .840 52.5 6.29 630 75.4 
4/8" 10.56 880 54.9 6.58 659 70.0 
39” 11.05 .920 57.5 6.89 690 82.6 
TIO" 11.54 .962 60.1 7.20 721 86.3 
arr 12.05 1.004 62.7 7.51 752 90.1 
40” 12.57 1.047 65.4 7.83 785 94.0 
AT 13.10 1.091 68.1 8.16 818 08.0 
4/2” 13.64 1.136 70.9 8.50 851 102.0 
4'3” 14.19 1.182 73.8 8.84 886 106.1 
44” 14.75 1.220 76.7 9.19 921 110.3 
4'5” 15.32 1.277 79.7 9.55 957 114.6 
46” 15.90 1.325 82.7 9.91 993 119.0 
Pid 16.50 1.375 85.8 10.28 1030 123.4 


4'8” 7ii1 1.425 89.0 10.66 1008 128.0 


54 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


PLraté G.—DIMENSIONS AND CONTENTS oF CYLINDRICAL TuBs.—Continued. 


When filled to When filled to 
--——_——1 inch depth —_—_, -——1 foot depth——— 
Bottom Volume Pounds Gallons Pounds Gallons 
Diameter area in of of oO fa) 
inside Sqranc: cit t water water water water 
4'9” 1772 1.477 92.2 11.05 1106 132.6 
4/10” 18.35 1.529 92.5 11.43 1145 137.3 
art 18.99 1.582 98.8 11.84 1185 142.0 
oes 19.64 1.636 102.15 12.24 1226 146.9 
eu 20.30 1.691 105.58 12.65 1267 151.8 
5.2” 20.97 1.748 109.07 13.07 1309 156.8 
ce 21.65 1.804 112.64 13.50 1352 161.9 
iw ke 22.34 1.862 116.22 13.93 1395 167.1 
Cae 23.04 1.920 119.88 14.37 1439 172.4 
6.4 23.76 1.980 123.59 14.80 1483 1770 
cotig 24.48 2.040 127.37 15.26 1528 183.1 
5/8” 25 22 2.102 131.21 15.72 1575 188.7 
Rites 25.07 2.164 135.09 16.19 1621 194.3 
S104 26.73 2297 139.04 16.66 1669 199.9 


Bri” 27.50 2.291 143.04 17.14 1716 205.7 


60” 28.26 . 2.356 147.09 17.63 1765 211.5 
wig oe 20.07 2.422 151.21 18.12 1814 217.4 
O27 29.87 2.489 155.38 18.62 1865 223.4 
O45 30.68 2.557 159.61 19.13 1915 220.5 
6'4” 31.50 2.626 163.89 19.64 1967 235.7 
G50 32.34 2.605 168.23 20.16 2019 241.9 
6'6” 33.18 2.765 172.63 20.69 2071 248.2 
iy <a 34.04 2.837 177.09 21.22 2125 254.6 
6'8” 34.91 2.909 181.59 21.76 2179 261.1 
reyes 35.79 2.982 186.17 22.31 2234 267.7 


6’10” 36.67 3.056 190.79 22.86 2289 274.3 
reap a4 37.57 Sak 195.47 23.42 2345 281.0 


7'0 38.49 3.207 200.21 23.99 2403 287.8 
ris 30.41 3.284 205.01 24.57 2460 294.8 
ie 40.34 3.362 209.86 25.15 2518 301.8 
7:3. 41.28 3-440 214.77 25.74 2577 308.8 
a AN 42.24 3.520 219.78 26.33 2637 315.9 
ae 43.20 3.600 224.75 26.93 2607 332.2 
7.0. 44.18 3.682 220.83 27.54 2758 330.5 
7 iy i 45.17 3.764 234.92 28.16 2820 337.90 


7'8” 46.16 3.847 240.16 28.78 2882 345.3 


DIAZOTIZATION OF ANILINE AND MANUFACTURE OF ORANGEG 55 


PLAtE G.—DIMENSIONS AND CONTENTS OF CYLINDRICAL TuBs.—Continued. 








When filled to When filled to 
lama —1 inch depth— —_ --——1 foot depth——— 
Bottom Volume Pounds Gallons Pounds Gallons 
Diameter area in of fe) Co) of 
inside Sq. ft. eu, ft. water water water water 
” 
7'9 47.17 3.931 245.41 29.41 2045 352.9 


8’0” 50.27 4.189 261.50 41.33 3138 376.0 
Ray 51.32 4.277 266.97 31.99 3204 383.9 
aS” 52.38 4.305 272.51 32.65 3270 301.9 
8'3” 53-46 4.455 278.10 33-32 3337 399.9 
8’4” 54-54 4.545 283.75 34.00 3405 408.0 
8'5” 55.64 4.637 2809.45 34.68 3473 416.2 
8’6” 56.75 4.729 205.21 35.37 3542 424.5 
re 57.86 4.822 301.03 30.07 3612 432.9 
88” 58.99 4.916 306.89 36.77 3683 441.3 
8'9” 60.13 5.011 312.83 37-49 3754 449.8 


9'0” 63.62 5.301 330.95 39.66 3971 475.9 
oie 64.80 5.400 337-12 40.40 4046 484.8 
9'2” 66.00 5.500 343.33 41.14 4120 493.7 


9'6” 70.88 5.907 368.75 44.19 4425 530.3 
i 72.13 6.011 375.20 44.97 4503 539.6 
98” 73-39 6.116 381.81 45-75 4582 549.1 


CHAPTERGIV: 


OTHER DYES PREPARED FROM DIAZOTIZED ANILINE. AMINO 
NAPHTHOL RED G, FAST ACID FUCHSINE B, CROCEINE 
ORANGE, CHROMOTROPE 2B, CHRYSOIDINE Y 
AND SUDAN I 


AMINO NAPHTHOL RED G’ 


Amino Naphthol Red G is prepared by coupling diazotized 
aniline with the acetylated 1:8:3:6 amino naphthol disulfonic 
acid ‘“H” in alkaline solution. 


N,Cl HO NHCOCH, 
Som 
[oe =i Ge eu. aad 
ee? NaSO, \/4\/ 0,SNa 
Diazo-I Acetyl ‘‘H’’ acid 


disodium salt 
— HO NHCOCH, 
ren 


Roe 
NaSO,\ 47\/0,SNa 
Amino Naphthol Red G 


Preparation of the Dye.— 


Acetyl “H” Acid Disodium Salt C,,H,O,NS,Na,, 
Molecular Weight = 405. 


Materials.— 
348 lbs. “H”’ acid monosodium salt, 100 per cent 
120 Ibs. caustic soda solution 40° Bé. 
750 lbs. water 
500 lbs. ice 
175 lbs. acetic anhydride, 100 per cent 
tub No. 3 


7 Also known as Azo Phloxine 2G, Erio Phloxine 2G Conc., and 6B Conc., Bril- 
liant Carmine 2G, etc. 


OTHER DYES PREPARED FROM DIAZOTIZED ANILINE 57 


300 Ibs. soda ash 
1,500 lbs. ice 
tub No. 8 
I lb. mol. Diazo-1 
tub No. 6 
1,250 lbs. salt 


Method.—Preparation of the dye includes the acetylation of 
“H” acid to form the component. A tub 5 feet in diameter and 
5 feet deep, fitted with an agitator to turn at a speed of thirty 
revolutions per minute (tub No. 3, Plate F), is used for dissolv- 
ing and acetylating the “H” acid. Tub No. 8 is used for the 
coupling as in the preparation of Orange G but must have an 
iron steam pipe installed for heating the charge prior to salting 
out the dye. 


Seven hundred and fifty pounds of water is run into tub No. 
3 filling to a depth of 7% inches, and the agitator started. A 
quantity of commercial “H” acid, in powder or paste form, 
equivalent to one molecule plus 2 per cent excess based on 341, 
the molecular weight of the monosodium salt of “H” acid, is 
entered. Solution is now made by gradually adding caustic soda 
solution in small amounts, up to 120 pounds of the caustic be- 
ing required to neutralize the quantity of commercial “H” acid 
taken. Any paste clinging to the sides of the tub is to be washed 
down, and the bottom of the tub probed for undissolved material. 
_A dark, opaque, liquor results, and addition of the caustic soda 
is halted as soon as solution is complete and a faintly alkaline re- 
action is shown by a test made with Brilliant Yellow paper. The 
solution should not have greater volume than that of 1,200 
pounds of water, and fill the tub to a depth of about 12 inches. 

Five hundred pounds of cracked ice is now entered and the 
temperature falls to below 7° C. One hundred and seventy-five 
pounds of acetic anhydride® is held in readiness, and turned into 
the tub in one addition, as soon as the ice has melted. The mix- 

8 Acetic anhydride is received in standard carboys holding 1oo pounds of the 98 
per cent material. <A slightly discolored anhydride is not objectionable provided that 


its strength is 98 per cent to 100 per cent. The manner in which the material is to 
be handled is identical with that directed for the use of muriatic acid in Chapter II. 


58 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


ture is allowed to agitate for thirty minutes and a test is then 
made to ascertain the completeness of acetylation. 

When a laboratory test shows the acetylation to be complete, 
150 pounds of soda ash is sprinkled into the acetyl “H” acid, 
slowly, taking an hour for the addition, to allow complete neu- 
tralization of the soda ash to carbonic acid and dissipation of 
the frothing. The solution is now delivered down to tub No. 8 
through a 3-inch hose, and 150 pounds of soda ash is entered, 
with only ordinary precautions, and the solution allowed to 
agitate while Diazo-1 is being prepared in tub No. 6, according 
to the directions given in Chapter III. 


When the diazo is ready, 1,500 pounds of cracked ice is added 
to the component in tub No. 8, bringing the temperature down 
below 5° C.; the diazo solution is run down onto the surface of 
the component, the flow being adjusted so as to take forty-five 
minutes for the addition and the coupling mixture being watched 
for excessive frothing and for the possibility of the top portion 
turning acid. Tub No. 6 is rinsed down and the coupling allowed 
to agitate until the following day. A test is made on the follow- 
ing morning for presence of the component in slight excess and 
precipitation of the dye made by heating to 55° C., and adding 
1,250 pounds of common salt to the heated charge. The extent 
of the salting and precipitation is tested and the charge then de- 
livered to a blow-case for pressure filtration. 


The finished charge should have a volume closely approximat- 
ing that of 7,000 pounds of water, and should be only faintly 
alkaline in reaction. Filtration is moderately rapid; the precipi- 
tated dye is somewhat voluminous and a one-molecule charge 
will fill a thirty-plate filter press several times. With air pres- 
sure of 40 pounds per square inch filtration should be com- 
pleted within twenty-four hours. The filtered cake is compact 
and firm but contains about 65 per cent of mother liquor. Drying 
must be conducted at about 60° C., as decomposition of the 
acetylamino group from the alkali present can occur with strong 
heating. 

Reaction between diazo benzene and the acetyl “H” acid pro- 
ceeds rather slowly, especially at very low temperatures. Dur- 


OTHER DYES PREPARED FROM DIAZOTIZED ANILINE 59 


ing the first six hours of agitation of the coupling mixture very 
little or no dye may be precipitated, but a large amount will be 
out of solution at the end of twenty hours’ agitation. Heating 
and salting precipitate the dye very completely; the heating im- 
proves the condition of the dye for filtration, but should not be 
carried beyond the limit indicated as there is danger of decom- 
posing the acetylamino group at higher temperatures, with con- 
sequent formation of off-shade colors. The test made on the 
finished coupling to determine the presence of a slight excess 
of the component is for verifying the exactness of the proportions 
taken, but is of no value to the charge immediately in question 
as no action can be taken at this stage of the process to remedy 
a deficit. This test, and also the test for completion of the salt- 
ing process, is performed similarly to the tests directed for 
Orange G, in Chapter III. Should there be question as to 
whether excess of the diazo has been taken, a test is made by 
treating 15 cc. of a sample in a test tube with a little dilute caustic 
soda solution and gently warming, when an odor of phenol would 
be noticed if the diazo or its decomposition products were present 
in the finished coupling, the same odor being noticeable in the 
charge after heating. 


Completeness of the acetylation of “H” acid is tested by taking 
10 cc. of a sample with some ice in a small beaker and acidifying 
with pure dilute hydrochloric acid; two drops of tenth normal 
nitrite of soda solution stirred in should be sufficient to form 
_ excess, shown by the blue coloration on starch potassium iodide 
paper, or when a drop of the solution thus prepared is streaked 
on a piece of filter paper and tested with a drop of a freshly pre- 
pared alkaline solution of “H” acid touched to the rim of the 
seepage, there should be no color formed at the juncture. If 
the tests show incompleteness of acetylation, 5 pounds of acetic 
anhydride may be added to the mixture in tub No. 3 and allowed 
to agitate for fifteen minutes, when another test is made; 175 
pounds of the anhydride should suffice for the acetylation or- 
dinarily. 

According to the molecular weight of the dye compound, 509 
pounds of pure dye constitutes the yield theoretically possible 


60 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


from a pound molecule charge. The dye is strongly reduced for 
the market, a typical selling strength being one composed of 40 
per cent pure dye and 60 per cent salt; on the basis of such re- 
duction the yield of the selling standard dye theoretically pos- _ 
sible is 1,272 pounds. ‘The yield to be obtained depends mainly 
upon the character of the “H” acid employed; with an “H” acid 
of consistently good quality, a twelve months’ average yield of 
go per cent of theory is to be obtained with the method. 

Amino Naphthol Red G is used as an acid dye for wool and 
silk. The shade produced on wool has been found very fast to 
light but only fairly so to washing. Production of this dye in 
the United States during 1920 totaled 132,637 pounds, valued at 
$1.78 per pound. 


FAST ACID FUCHSINE B 


Prepared by coupling diazotized aniline with the 1:8:3:6 
amino naphthol disulfonic acid ‘“H” in alkaline solution. 


N,Cl HO NH, 


Cae lk. 
So NaSO NOON Ose a 


Diazo-1 fH? acid 
Pee HO NH 
Mie N=N ae 


disodium salt 
etd 
NaSO,\ 4\ 40,SNa 
Fast Acid Fuchsine B 


Preparation of the Dye.— 


“H” Acid Disodium Salt, C,,H,O,NS,Na,, 
Molecular Weight = 363 
Materials.— 
348 lbs. “H” acid monosodium salt, 100 per cent 
55 lbs. soda ash 
750 lbs. water 
tub No. 3 
150 Ibs. soda ash 
1,000 lbs. ice 


OTHER DYES PREPARED FROM DIAZOTIZED ANILINE 61 


tub No. 8 
1 Ib. mol. Diazo-1 
tub No. 6 
1,000 lbs. salt 


Method.—The set of tubs used in preparation of this dye is the 
same as for that of Amino Naphthol Red G, and the method 
follows a similar procedure. 


Seven hundred and fifty pounds of water is entered in tub No. 
3. The “H” acid, in quantity equivalent to one-pound molecule 
plus 2 per cent excess, is entered and dissolved by addition of 
up to 55 pounds of soda ash sprinkled in slowly; solution takes 
place easily and the use of excess soda ash at this point is not 
specifically injurious, as more is to be added later. The solution 
of the component is delivered to tub No. 8 through a 3-inch hose, 
and tub No. 3 is rinsed down. One hundred and fifty pounds of 
soda ash is entered in the component in tub No. 8 and allowed to 
dissolve while Diazo-1 is being prepared in tub No. 6 as directed. 

When the diazo is ready, 1,000 pounds of cracked ice is entered 
in tub No. 8, bringing the temperature down to 5° C., and the 
solution of the diazo is run down onto the surface of the com- 
ponent, taking forty-five minutes for its addition, the coupling 
mixture being watched for the possibility of an acid condition 
occurring in streaks or layers; if such should happen, addition of 
the diazo is halted for a short time and the coupling allowed to 
agitate until it is again homogeneously alkaline, and the addition 
then resumed. When the diazo solution has all been added 
agitation is continued for three hours, when the completeness of 
the reaction may be tested; it is usually the practice to allow 
such a coupling to continue agitating until the following day, 
as a charge cannot be conveniently coupled and finished within 
the working hours of one day. The dye is largely in solution 
and is salted out by addition of 1,000 pounds of common salt 
and delivered to a blow-case for pressure filtration. 

The finished charge should have the volume of approximately 
5,000 pounds of water; the reaction, tested with Brilliant Yellow 
paper, should be only slightly alkaline, corresponding to the bi- 


62 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


carbonate condition. The precipitated dye is crystalline in char- 
acter and filters fairly well, a cake containing about 50 per cent 
of liquid being obtained. Drying is without points of special 
difficulty. 

Coupling between diazo benzene and alkaline “H” acid takes 
place readily, and if it is desired to economize on time, the prog- 
ress of the coupling may be tested after fifteen minutes’ agitation 
and as soon as the laboratory test on a sample of the charge 
shows the diazo to be completely utilized, the salt may be added 
and the charge finished. An alkaline solution of “H” acid for 
use in a coupling must be prepared on the day when used; 
economy of time in conducting the process cannot be obtained 
by dissolving on the day previous to use as ““H” acid decomposes 
slowly in alkaline solution, the decomposition being greater in a 
solution made with caustic soda than when soda ash is used. 


Fast Acid Fuchsine B dyes wool and silk easily and level in 
acid bath, with a blue red shade. The dye is little used of itself 
having been largely replaced by other combinations because of 
its comparatively lesser fastness to light. It finds a certain 
amount of use for shading other dyes. Production of the dye in 
the United States during 1920 totaled 30,678 pounds, valued at 
$1.65 per pound; during 1919 the production amounted to 26,699 
pounds valued at $1.69 per pound. 


CROCEINE ORANGE?’ 


Prepared by coupling diazotized aniline with the 2:6 naphthol 
monosulfonic acid, or Schaeffer Salt, in alkaline solution. 


N,Cl Nae se eae 

PORES OD. as OH “~~ 

Loon’) Gla te yheer | scenal eer 
NaSO,\/\/ a NaSO,\/\/ 

Schaeffer Salt Diazo-1 Croceine Orange 


Preparation of the Dye.— 
Schaeffer Salt, C,,H,O,SNa, Molecular Weight = 246. 


® Also known by the GR and Y marks, and as Brilliant Orange G, Pyrotin 
Orange, Orange GR, X and ENL, Ponceau 4GB, etc. 


OTHER DYES PREPARED FROM DIAZOTIZED ANILINE 63 


Materials.— 


252 lbs. Schaeffer Salt, 100 per cent 
2,500 lbs. water 


tub No. 3 
150 lbs. soda ash 
1,500 lbs. ice 
tub No. 8 
I lb. mol. Diazo-1 
tub No. 6 


1,500 lbs. salt 


Method.—The set of tubs used in preparation of this dye is 
the same as for that of Amino Naphthol Red G. An iron steam 
pipe is to be installed in tub No. 3 for heating to dissolve the 
component. 

Two thousand five hundred pounds of water is run into tub 
No. 3, filling to a depth of 25 inches. A quantity of Schaeffer 
Salt, in powder or paste form, containing one mol. plus 2 per 
cent excess, based on the molecular weight of the sodium salt, 
or 252 pounds of the 100 per cent material, is added. A small 
amount of caustic soda solution is added to insure a slightly alka- 
line condition in the mixture, and solution made by heating to 
75° C., with direct steam. The temperature is maintained for 
one-half hour to complete solution and the component then de- 
livered to tub No. 8 and allowed to agitate and cool over night. 
On the following day, 150 pounds of soda ash is added and 
allowed to dissolve while Diazo-1 is being prepared in tub No. 
6 according to the directions previously given. 

When the diazo is ready, from 1,500 to 2,000 pounds of 
cracked ice is entered in tub No. 8 to bring the temperature of 
the component down to 5° C.; the amount of ice to be used de- 
pends upon the extent to which the component shall have cooled 
from agitation over night. The solution of the diazo is then 
run down onto the surface of the component, taking forty-five 
minutes for its addition and exercising ordinary precaution to 


64 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


prevent excessive foaming in the coupling tub. The coupling 
is allowed to agitate for four hours, after which time it may be 
tested for completion of the reaction. About 1,500 pounds of 
salt is to be used for precipitation of the dye, the addition being 
made gradually after the first 500 pounds have been entered, and 
the extent of the precipitation observed after each addition. 
The finished charge is delivered to a blow-case for pressure fil- 
tration. The final volume of the charge should not be much 
greater than that of 8,000 pounds of water; a reaction testing 
very slightly alkaline to Brilliant Yellow test paper is favorable 
to precipitation of the dye to a good condition for filtration. 


A difficulty in preparing this dye is found in the low solubility 
of the component; at ordinary temperatures, Schaeffer Salt is 
soluble to the extent of only 5 per cent, necessitating a fairly 
large volume for complete solution. The method makes use of the 
component in a state of partial suspension, a part of the Schaeffer 
Salt being out of solution at the commencement of the coupling 
reaction. The precipitated material is in a fine state of division 
and is ultimately engaged in reaction with the diazo. The final 
volume is necessarily somewhat large, with disadvantage to the 
complete precipitation of the soluble dye. 


The dye is used in acid bath for wool and silk. It dyes these 
fibers easily and level, with good light fastness in the shade pro- 
duced, and has also some use in the dyeing of vegetable fibres 
and in the fabrication of lake pigments. The production of 
Croceine Orange in the United States during 1919 amounted to 
17,274 pounds, valued at $0.88 per pound, with a considerably 
increased production in 1920, amounting to 96,573 pounds, valued 
at $1.04 per pound. 


CHROMOTROPE 2R 


Prepared by coupling diazotized aniline with the 1:8:3:6 
dioxy naphthalene disulfonic or chromotropic acid, in alkaline 
solution. 


OTHER DYES PREPARED FROM DIAZOTIZED ANILINE 65 


N,Cl OH OH 
AN ie ‘apn 
aes Reo AN oun: 
Diazo-1 Chromotropic acid 


disodium salt 
OH OH 
FO de I ON. 


| | 
mA : NaSo\/ \/ 0,8Na 


Chromotrope 2R 


Preparation of the Dye.— 


Chromotropic Acid Disodium Salt, C,,H,O,S,Na,, 
Molecular Weight = 364. 
Materials.— 
371 lbs. chromotropic acid disodium salt, 100 per cent 
2,500 lbs. water 


tub No. 3 
200 lbs. soda ash 
1,000 Ibs. ice 
tub No. 8 
1 lb. mol. Diazo-1 
tub No. 6 


750 Ibs. salt 


Method.—Preparation of this dye follows the same general 
routine as that of Croceine Orange. The component is to be 
dissolved in tub No. 3 and delivered to tub No. 8, where coupling 
is made, and the finished charge salted out and delivered to a 
blow-case for pressure filtration. The dye produces a fuchsine 
red shade on wool in acid bath, but is of poor fastness, and is 
used chiefly for shading other dyes. The statistics as to amounts 
produced are not available. 


CHRYSOIDINE Y 


Prepared by coupling diazotized aniline with meta phenylene 
diamine in neutral solution, with subsequent precipitation of the 
hydrochloride salt of the dye in acid solution. 


66 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


N,Cl NH, NH, 


Gi ean ; 
NOs \/NH, NY \ / NH, HCl 


Diazo-1 Meta Chrysoidine Y 
phenylene 
diamine 


Preparation of the Dye.— 
Meta Phenylene Diamine, C,H,N,, Molecular Weight = 108. 


Materials.— 
110 lbs. meta phenylene diamine, in the form of 2 per cent 
solution 
3,000 lbs. ice 


tub No. 5 
30 lbs. soda ash 
300 Ibs. water 
tub No. 1 
1 Ib. mol. Diazo-1 
| tub No. 2 


150 lbs. muriatic acid 
1,500 lbs. ice 


Method.—A tub 8 feet in diameter and 6 feet deep (tub No. 5, 
Plate F), with capacity for holding 18,000 pounds of water, and 
located on the second floor, is used both for preparation of the 
component and for coupling; the agitator should be geared to 
turn at a speed of thirty revolutions per minute, and should be 
of sturdy construction for carrying the heavy load; a wooden 
steam pipe is to be secured to the inside wall of the tub, for 
heating, and a similar wooden pipe is used for conducting the 
diazo solution to the bottom of the tub; these pipes should be 
protected with flanking side boards to alleviate splashing during 
agitation. A tub 5 feet in diameter and 5 feet deep, fitted with 
agitator to turn at a speed of thirty-six revolutions per minute 
(tub No. 2, Plate F), is to be used for preparation of the diazo. 
A small tub 3 feet in diameter and 3 feet deep, located on the third 
floor (tub No. 1, Plate F), is used to contain a solution of soda 


OTHER DYES PREPARED FROM DIAZOTIZED ANILINE 67 


ash. Filtration is to be made by vacuum, using a suction filter 
tub 7 feet in diameter and 18 inches deep, located on the raised 
center portion of the first floor (Plate F). 


A quantity of a solution of meta phenylene diamine containing 
110 pounds of the 100 per cent material, or one mol. plus 2 per 
cent excess, is pumped from storage into tub No. 5. The specific 
gravity of such a solution is very nearly the same as that of 
water, and in the case of a 2.00 per cent solution, the amount re- 
quired would be 5,500 pounds, filling the tub to a depth of 21 
inches, any appreciable difference in volume from that of water 
being closely compensated by the displacement due to the agita- 
tor; as the amount of the component taken is determined by 
measurement of the volume and analysis of the solution, the 
exact diameter of the tub must be known, in this case, 8 feet; 
displacement due to the agitator is about 1 per cent of the total 
volume. The solution is held in readiness for the subsequent 
coupling. 

A solution of soda ash is made by running in 300 pounds of 
water in tub No. 1, filling to a depth of 8 inches, and dissolving 
30 pounds of technical soda ash; the solution made is held in 
readiness. Diazo-1 is then made up, in general, according to the 
directions given in Chapter III, but using tub No. 2 instead of 
tub No. 6; for the diazotization, a barrel with a spigot at the 
bottom must be improvised for holding the nitrite of soda solu- 
tion, and secured on a platform or deck on top of tub No. 2; 
the nitrite solution is delivered onto the surface of the aniline 
hydrochloride, and the solution of the diazo fills tub No. 2 to a 
depth of about 30 inches when completed. 


While Diazo-1 is being prepared, 3,000 pounds of cracked ice 
is entered in tub No. 5 to bring the temperature down to 0° C. 
Coupling is then commenced by running the solution of the diazo 
to the bottom of tub No. 5, through a 3-inch hose connected to 
the wooden pipe. When about Io per cent of the diazo solution 
has been run down, the solution of soda ash held in tub No. 1 
is also started flowing, onto the surface of the coupling mixture. 
Forty-five minutes is to be allowed for addition of the diazo, and 
the flow of the soda ash solution timed so as to finish shortly 


68 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


after that of the diazo, the coupling being watched towards the 
end of the period for excess of the diazo, by spotting out a drop 
of the coupling on a piece of filter paper and testing the rim of 
the seepage with a drop of the diazo solution, a red brown line 
showing presence of the diamine in excess. The reaction of the 
coupling should not be allowed to turn alkaline by too rapid ad- 
dition of soda ash, and the temperature during the coupling 
should not be allowed to rise above 2° C., unmelted ice remain- 
ing in the charge until most of the diazo has been added. When 
addition of the diazo is complete, tub No. 2 is carefully rinsed 
out to prevent formation of traces of phenolic matter from de- 
composition of any diazo remaining, and the washings run into 
the sewer; this detail insures a clean tub for the next day’s 
charge. The charge is agitated for one hour and then tested for 
the presence of the component in slight excess. Muriatic acid 
is now added until a distinctly mineral acid reaction is shown by 
a test made with Congo Red paper, about 150 pounds of the 20° 
Bé. acid being required, and the temperature brought to 65° C., 
by passing in steam slowly for two hours; the heating converts 
the iminoazo form of the coupling into the azo; too rapid heating 
causes excessive foaming in the charge. One thousand five 
hundred pounds of salt is added to the heated charge to precipi- 
tate the dye; a test is made for completeness of the precipitation 
and the charge then delivered to a suction filter. Filtration is 
very rapid, the entire charge being taken on one filter bed and 
no vacuum being required until the end of the filtration, when the 
vacuum is to be applied and the charge pressed out with a hand 
float to remove residual mother liquor. 

The final volume attained in the charge is close to that of 
13,000 pounds of water, filling the coupling tub to a depth of 
about 50 inches; the dye precipitates in the form of steel blue 
needles and the filtered product should contain as low as 15 per 
cent moisture, resembling moist sand in substance. A filter tub 
used for this dye cannot be used for the filtration of other colors 
without severe washing, due to the contamination of the wood 
by the color. Drying is conducted on wooden trays, at a low tem- 
perature. The dye should be free from tarry matter; such tar 


OTHER DYES PREPARED FROM DIAZOTIZED ANILINE 69 


may result, from excess soda ash used during the coupling, or 
from an excess of diazo taken through error in calculation of 
the quantity of the component, as the percentage content of a 
diamine liquor varies somewhat from day to day and exact an- 
alysis is necessary for each charge; the tar may also result from 
an undue rise in temperature during coupling, or from use of a 
poor grade of diamine liquor, in which the tar is present as im- 
purity. 

Two hundred and forty-eight pounds of pure dye constitutes 
the yield theoretically possible from a molecule charge, according 
to the molecular weight of the dye compound, the mono hydro- 
chloride of benzene azo diamino phenyl. Chrysoidine Y is mark- 
eted in various strengths, including the “ordinary” and the 
“Extra” or concentrated. Typical selling strengths of good repute 
would be those in which the ordinary consists of one part pure 
dye and one part salt, and for the Extra, two parts pure dye and 
one part salt. Considerable variation of selling standards is to 
be met with, as the dye is one of the cheap staples of the in- 
dustry and is much dealt in. On the basis of the reductions men- 
tioned, the yields of market dye theoretically possible from a 
molecule charge would be 496 pounds of the ordinary or 372 
pounds of the Extra. An average yield of go per cent of the 
theory is to be obtained with the method. A cause of low yield 
lies in the use of diamine liquors of low percentage, 1.5 per 
cent and below, giving a large final volume and necessitating the 
use of extra salt, which cannot prevent some loss of the dye in 
the mother liquor and is accompanied by a lowering in strength 
of the dye. , 

The method directs the use of the meta phenylene diamine in 
the form of a liquor, as this intermediate will ordinarily be manu- 
factured in the factory where used, and handled in the form of 
a solution. A method for the use of pure solid meta phenylene 
diamine as component would involve the preparation of its 5 
per cent solution in tub No. 3, Plate F, using just sufficient 
muriatic acid to obtain an acid reaction, and delivering the solu- 
tion to tub No. 5 for coupling; acetate of soda should be substi- 
tuted for the soda ash, in amount proportionate to the quantity 


70 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


of mineral acid to be neutralized, and the coupling then conducted 
in a sequence similar to that described above. The use of solid 
meta phenylene diamine offers less difficulty in control, but as the 
dye is cheap, economy in the cost of materials favors the use of 
the technical liquor. 

Chrysoidine Y is much used for dyeing of cotton, with as- 
sistance of a mordant, an orange shade being produced. It can 
also be used for wool, silk, leather and oils, and is non-toxic when 
taken internally. It is of poor fastness in general. Production 
in the United States in 1920 totaled 585,648 pounds valued at 
$0.87 per pound, and in 1919, 314,581 pounds valued at $1.04 per 
pound. 


SUDAN I° 


Prepared by coupling diazotized aniline with beta naphthol in 
alkaline solution. , 


N,Cl ee 
/\/\0Na an /\/\08 
| oteae: oe eo hal sagly cael eee™ a cole eer 
| Pee Be 

Sodium Diazo-1 Sudan I 


beta naphtholate 
Preparation of the Dye.— 
Beta Naphthol, C,,H,O, Molecular Weight = 144. 


Materials.— 
147 lbs. beta naphthol, technically pure 
120 lbs. caustic soda solution, 40° Be. 
2,000 lbs. water 


tub No. 3 
100 lbs. soda ash 
1,000 Ibs. ice 
tub No. 6 
1 lb. mol. Diazo-1 
tub No. 2 


75 lbs. acetate of soda 


10 Other names for this dye are Fast Soluble Orange, Spirit Orange, Scarlet B, 
Oil Yellow; the article found on the market usually bear a special name given by 
each manufacturer. 


OTHER DYES PREPARED FROM DIAZOTIZED ANILINE ah 


Method.—A tub 5 feet in diameter and 5 feet deep, with agi- 
tator to turn at a speed of thirty revolutions per minute (tub No. 
3, Plate F), is used for dissolving the component; coupling is 
made in a tub 6 feet deep and 6 feet in diameter, located on the 
second floor; tub No. 6 may be used for the coupling, with an 
agitator geared to turn at a speed of forty revolutions per minute. 
The diazo is to be prepared in tub No. 2, Plate F, under the same 
conditions as for use in preparing Chrysoidine Y. Filtration is 
made by vacuum, using a suction filter tub located on the first 
floor. 


Two thousand pounds of water is run into tub No. 3, filling toa 
depth of 20 inches. One hundred and forty-seven pounds of tech- 
nical beta naphthol, equal to one mol. plus 2 per cent excess, is 
added, followed by 120 pounds of caustic soda solution of 40° 
Bé. density, and solution made by heating to 70° C., and main- 
taining the temperature for thirty minutes; the solution is allowed 
to agitate over night, to cool to room temperature, and on the 
following day is delivered to tub No. 6 where 100 pounds of soda 
ash is added and allowed to agitate until Diazo-1 has been pre- 
pared. 


Diazo-1, prepared in tub No. 2, is further treated with 75 
pounds of acetate of soda, to decompose the excess of muriatic 
acid. The component in tub No. 6 is cooled to 5° C., by addition 
of 1,000 pounds of cracked ice, and the diazo solution then 
started flowing down onto the surface of the component, more 
slowly than is usually the case, taking seventy-five minutes for 
the time of addition and using an additional 500 pounds of ice 
to hold the temperature of the diazo solution at 2° C., if neces- 
sary. ‘The dye precipitates on formation and the coupling re- 
action is complete practically as soon as all of the diazo has been 
added and the diazotization tub rinsed down. A test is made for 
the completeness of the reaction and the charge run to a filter 
tub; filtration is very rapid in a well prepared charge; the filtered 
cake should be given two efficient washings from a shower ar- 
ranged over the tub, to remove inorganic salts and alkalies, press- 
ing out the residual liquor with a hand float after each washing. 
Drying should be conducted at a very low temperature, open air 

6 


72 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


drying by placing the pans of dye on the top of the drying ovens 
being adequate. The dye dries easily to a friable powder, easily 
pulverized. 

The final volume is of little importance in the case of this dye. 
Points necessary for observance to obtain the yield include the 
neutralization of the free mineral acid of the diazo, in order to 
avoid precipitation of the beta naphthol, and, for the same reason, 
delivery of the diazo solution to the component in a fine stream 
under very good agitation; any appreciable amount of mineral 
acid accumulating in the coupling mixture precipitates beta naph- 
thol forming a gummy mass in the dye, with resultant lowered 
yield and great difficulty in handling the finished charge; reten- 
tion of the beta naphthol in solution can be insured by taking up 
to one molecule excess of the caustic soda when dissolving, such 
practice giving a product which filters easily but with lowered 
yield due to a certain amount of decomposition in the diazo, and 
the procedure is not satisfactory. 


The molecular weight of the dye compound is 248; a yield of 
practically theoretical amount of dye should be obtained, with 
allowance only for slight mechanical loss in handling. The dye 
is variously reduced for the market, with oil soluble materials, 
and finds use in coloring spirit lacquers and oils, a yellowish red 
shade being obtained. It is of moderate importance in the in- 
dustry, the production in the United States amounting to 116,624 
pounds, valued at $1.21 per pound, for 1920 and 75,868 pounds, 
valued at $1.28 per pound, in 19109. 


CHAPTER V 


DIAZOTIZATION OF THE HOMOLOGUES OF ANILINE AND MANU- 
FACTURE OF PONCEAU 2R, SUDAN II AND 
BRILLIANT ORANGE 0 


Diazotization of Meta Xylidine.1:— 


Meta Xylidine, C,H,,N, Molecular Weight = 121. 


NH, N,Cl 

/\CH, CH, 

Salil ih age 

DG SA 
CH, She Gy 

Meta xylidine Diazo xylene chloride 
Materials — 
121 lbs. meta xylidine, = 1 mol. 


345 lbs. muriatic acid, 20° Bé. 
2,500 lbs. ice 
tub No. 6 
72 |bs. technical nitrite of soda 
300 lbs. water 
tub No. 4 


Method.—A tub 6 feet in diameter and 6 feet deep, fitted with 
an agitator to turn at a speed of thirty revolutions per minute 
(tub No. 6, Plate F’), is used for solution of the amine and for 
diazotization, as in the preparation of Diazo-1. A nitrite of soda 
solution, prepared by dissolving 72 pounds of technical nitrite 
of soda in 300 pounds of water, is held ready for use in tub No. 
4, Plate F. 

One thousand pounds of cracked ice is entered in tub No. 6 
with the agitator stopped. One hundred and twenty-one pounds 
of meta xylidine is entered on top of the ice and followed by 


11/To be referred to as Diazo-2. 


74 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


345 pounds (3 mols.), of muriatic acid; about 250 pounds of 
water is run in to start liquidation of the mixture and the agitator 
is then carefully started. The nitrite of soda solution held in tub 
No. 4 is now delivered onto the surface of the agitating mixture 
in tub No. 6 and at the same time, 1,000 pounds of ice is slowly 
fed into the tub. The flow of the nitrite liquor is adjusted so as 
to take thirty minutes for completion, after which tub No. 4 is 
to be rinsed down and the agitation continued for fifteen minutes. 
Five hundred pounds of ice is added to maintain the temperature 
at o° C., and the agitation is halted until use of the diazo in a 
coupling has been commenced. The solution is tested for com- 
plete utilization of the amine according to the directions for test- 
ing of Diazo-1 in Chapter III. The final volume of the diazo 
solution should not be greater than that of 3,500 pounds of 
water, filling the tub to a depth of about 24 inches. — 

The diazotization of meta xylidine differs from that of aniline 
in that a larger proportion of mineral acid and a greater rigidity 
in control of the temperature is necessary for the best result. 
The diazo is much less stable than is the case when aniline is 
being diazotized, and the volume attained will normally be 
greater than that of Diazo-1 due to the increased amount of ice 
required to maintain the lower temperature. An ideal method 
for the preparation of such unstable diazos would call for re- 
striction of the volume to a greater degree than is possible in 
the factory, where, to maintain a low temperature by addition 
of ice, the volume is necessarily a secondary consideration. 

Diazo xylene exhibits a less intense reactivity for coupling than 
does diazo benzene, hence its use is limited to combination with 
components which couple easily; the coupling is best made in a 
concentrated condition. The diazo finds use industrially in the 
manufacture of two important dyes. 


PONCEAU 2R 


Prepared by coupling diazotized meta xylidine with the 2: 3:6 
naphthol disulfonic acid, or “R” salt, in alkaline solution. 


DIAZOTIZATION OF THE HOMOLOGUES OF ANILINE 75 


N,Cl 
Baie? aoe, 
| cle | ariel te 
Bee 7 O),NaA) NZ 
CH, 
ok yt -salt Diazo-2 


"e \/\0H / NCH, 
rwaso\ A 50, Na 4 


Ponceau Re 
Preparation of the Dye.— 
“R” Salt, C,,H,O,S,Na,, Molecular Weight = 348. 


Materials— 


355 lbs. “R” salt, 100 per cent 
2,000 lbs. water 


tub No. 3 
200 lbs. soda ash 
1,000 lbs. ice 
tub No. 8 
1 lb. mol. Diazo-2 
tub No. 6 


1,000 lbs. salt 


Method.—A tub 9g feet in diameter and 6 feet deep, fitted with 
an agitator to turn at a speed of thirty revolutions per minute, 
and provided with an iron steam pipe (tub No. 8, Plate F), is 
used for the coupling. A tub 5 feet in diameter and 5 feet deep, 
tub No. 3, Plate F, is used to dissolve the component. 


Two thousand pounds of water is entered in tub No. 3 by 
filling to a depth of 20 inches. A quantity of “R” salt equal to 
one mol. plus 2 per cent excess, or 355 pounds of the 100 per 
cent material, in powder or paste form, is added and solution 
made by agitating at a temperature of 60° C., for thirty minutes. 
The solution should be slightly alkaline or at least neutral; any 
acidity shown should be neutralized by addition of sufficient 


76 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


caustic soda solution to give the solution a faintly alkaline re- 
action to Brilliant Yellow test paper. The component is de- 
livered to tub No. 8 and allowed to cool with agitation over night. 
On the following day 200 pounds of soda ash is added and dis- 
solved while Diazo-2 is being prepared in tub No. 6 according to 
the method previously given. 


When the diazo is ready, 1,000 pounds of ice is added to the 
component in tub No. 8 to bring the temperature to 5° C., and 
the diazo solution is then delivered onto the surface of the com- 
ponent, the flow of the diazo being adjusted so as to be com- 
pleted within forty-five minutes and the coupling being watched 
for excessive frothing. Agitation is continued until the next day 
when a control test is made to confirm the exactness of the pro- 
portions taken. The temperature of the charge is then brought 
to 85° C., by heating with direct steam and the dye is completely 
precipitated from the hot solution by gradual addition of about 
1,000 pounds of salt, the extent of precipitation being tested at 
the tub during addition of the salt. The temperature is to be 
maintained at 85° C., until the charge has been delivered to the 
blow-case for filtration. 


The final volume of the charge should not be greater than that 
of 7,000 pounds of water and the reaction should be neutral 
almost to the point of acidity. The precipitated dye is volumi- 
nous and non-crystalline in character, filtering poorly in general 
but best while hot. To minimize the time of filtration and take 
advantage of the temperature as far as possible, two blow-cases 
and the corresponding filter presses should be brought into ser- 
vice for the charge. The filtered dye contains a high percentage 
of moisture and drying consumes a fairly long period. 


The style Ponceau 2R originally referred to a dye prepared 
from pure meta xylidine and pure “R” salt. These intermediates 
are also used in the unpurified condition for the manufacture of 
brands of Ponceau 2R and a variety of strongly reduced products 
are marketed. The dye is used on wool for production of a 
shade of red of excellent fastness towards acids but less fast 
towards light and washing. The production in the United States 
during 1920 amounted to 1,286,002 pounds, valued at $0.80 per 


DIAZOTIZATION OF THE HOMOLOGUES OF ANILINE a, 


pound; in 1919 the production amounted to 552,680 pounds, 
valued at $0.80 per pound; the statistics of production undoubt- 
edly include all grades of the dye as the market product pre- 
pared from very pure intermediates is usually quoted at several 
dollars per pound. 


SUDAN II 


Prepared by coupling diazotized meta xylidine with beta 
naphthol in alkaline solution. 


Materials.— 
147 lbs. beta naphthol, technically pure 
120 lbs. caustic soda solution, 40° Bé. 
2,000 lbs. water 


tub No. 3 
150 lbs. soda ash 
1,000 lbs. ice 
tub No. 6 
1 lb. mol. Diazo-2 
tub No. 2 


150 lbs. acetate of soda 


Method.—The procedure to be followed in this preparation is 
similar to that outlined for the preparation of Sudan I, Chapter 
IV, the diazo being prepared in tub No. 2 on the third floor. 
Coupling is made in tub No. 6 on the second floor to facilitate 
delivery of the finished charge to a suction filter tub located on 
the first floor. The component is to be dissolved on a day pre- 
ceding its use and allowed to cool by standing over night. The 
purity of the product and the yield is influenced by conditions 
as in the case of Sudan I. The dye is used in oils and spirit 
lacquers to produce a yellowish red shade. It is of considerable 
importance, the production in the United States during 1920 
amounting to 170,658 pounds, valued at $1.43 per pound. Other 
names for the dye include Scarlet G, Moti Red G, Pyranalot R, 
Ponceau insoluble de Xylidine, etc. 


78 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


BRILLIANT ORANGE O 


Prepared by coupling diazotized ortho toluidine with the 2:6 
naphthol sulfonic acid, or Schaeffer salt, in alkaline solution. 


N,Cl N====N 
/\/\ 08 /N CH /\/N0H NCH, 
pei] sar 
NaSO, \. yay as yy,  asO\ he 
Schaeffer salt Diazo-3 Brilliant Orange O 


Preparation of the Dye.— 
Materials.— 


252 lbs. Schaeffer salt, 100 per cent 
2,500 lbs. water 


, tub No. 3 
200 lbs. soda ash 
1,500 lbs. ice 
tub No. 8 
1 lb. mol. Diazo-3 
tub No. 6 


1,500 lbs. salt 


Method.—In the preparation of this dye, 107 pounds of ortho 
toluidine (1 mol.) is to be diazotized'? in tub No. 6, Plate F, 
in the manner outlined for the preparation of Diazo-2, using 
three molecules of mineral acid and maintaining the temperature 
at o° C., until use of the diazo in a coupling has been started. 
The diazo from ortho toluidine is less stable than that from ani- 
line and the tendency towards formation of the imino-azo com- 
pound is greater than in the diazotization of aniline. The work 
of coupling and treating the dye is conducted according to the 
directions given for the preparation of Croceine Orange, Chapter 
IV, the tubs being used in the same sequence. Brilliant Orange 
O is produced for the purpose of utilizing excess stocks of ortho 
toluidine. The dyeing qualities are closely similar to those of 
the Croceine Orange. 


12 To be referred to as Diazo-3. 


DIAZOTIZATION OF THE HOMOLOGUES OF ANILINE 79 


The diazotization of meta toluidine is not undertaken for in- 
dustrial purposes. The diazotization of pseudo cumidine, 
Diazo-4, is conducted similarly to that of meta xylidine and ortho 
toluidine; coupling with “R” salt to form Ponceau 3R requires 
the same proportion of materials and similar procedure as for 
the preparation of Ponceau 2R. Para toluidine is only seldom 
diazotized ; the following method may be applied to prepare the 
diazo, for use in coupling with resorcin or beta naphthol to form 
spirit soluble dyes. 


Diazotization of Para Toluidine.t°— 
Para Toluidine, C,H,N, Molecular Weight = 107. 


NH, N,Cl 
hag = ea! 
Bo 
CH, 
Para toluidine Diazo toluene chloride 


Materials.— 
107 lbs. para toluidine, = 1 mol. 
250 lbs. muriatic acid, 20° Bé. 
400 lbs. water 


tub No. 3 
2,500 Ibs. ice 
tub No. 6 
72 lbs. technical nitrite of soda 
300 Ibs. water 
tub No. 4 


Method.—A tub 6 feet in diameter and 6 feet deep, fitted with 
an agitator to turn at a speed of thirty revolutions per minute 
(tub No. 6, Plate F), is used for diazotization, as in the case of 
the diazos previously discussed. A tub 5 feet in diameter and 5 
feet deep, provided with a wooden steam pipe (tub No. 3, Plate 
F), is used for dissolving the amine. A nitrite of soda solution, 
prepared by dissolving 72 pounds of technical nitrite of soda in 
300 pounds of water in tub No. 4, is to be held in readiness. 


13 Diazo-s. 


80 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


To prepare the amine for diazotization, 400 pounds of water 
is entered in tub No. 3 by filling to a depth of 4 inches. Two 
hundred and fifty pounds of muriatic acid, or two mols. plus 20 
pounds excess, is then added and followed by 107 pounds of 
para toluidine. Solution is made by agitating at 45° C., for 
thirty minutes. 

Three hundred pounds of water is now entered in tub No. 6 
by filling to a depth of 2 inches; 500 pounds of cracked ice is 
added and the agitation started. The solution of para toluidine 
hydrochloride in tub No. 3 is delivered onto the cooling mixture 
in tub No. 6, with an additional 500 pounds of ice to maintain 
the low temperature and precipitate the hydrochloride in a fine 
state of division. Diazotization is then made at a temperature 
below 2° C., by addition of 1,000 pounds of cracked ice and de- 
livery of the nitrite of soda solution from tub No. 4 onto the 
surface of the agitating mixture, the flow of the nitrite liquor 
being adjusted so as to be completed within thirty minutes; agita- 
tion is continued for fifteen minutes, when the diazotization may 
be considered complete. Five hundred pounds of ice is held in 
readiness to maintain the temperature at 2° C., until use of the 
diazo in a coupling is commenced. 

The final volume of the diazo solution should be that of ap- 
proximately 3,000 pounds of water. Complete utilization of the 
amine is tested for as in the case of Diazo-1. Only a slight ex- 
cess of mineral acid over the amount theoretically necessary for 
diazotization is to be taken as the tendency toward formation of 
the imino azo compound is not very marked. The diazo from 
para toluidine is slightly more stable than that from aniline but 
exhibits about the same degree of activity for coupling. The 
relatively high cost of pure solid para toluidine limits its use for 
manufacture of commercial azo dyes. The chrome color Flava- 
zene is probably the most notable of the para toluidine azo deriva- 
tives, and is prepared by coupling Diazo-5 with salicylic acid in 
alkaline solution under conditions similar to those outlined for 
the preparation of Alizarine Yellow R,‘in a later chapter. 


CHAPTER VI 


DIAZOTIZATION OF THE NITRO ANILINES AND MANUFACTURE 
OF ALIZARINE YELLOW R, PARA NITRANILINE 
RED, AND ALIZARINE YELLOW GG 


Diazotization of Para Nitraniline.1+— 
Para Nitraniline, C,H,O,N,, Molecular Weight = 138. 


NH, N,Cl 
o Fe 
a wees 
NO, NO, 
Para nitraniiine Diazo nitro benzene chloride 


Materials.— 
138 lbs. para nitraniline, 100 per cent = 1 mol. 
230 Ibs. muriatic acid, 20° Bé. 
650 lbs. water 


tub No. 3 
290 Ibs. muriatic acid, 20° Bé. 
1,500 lbs. ice 
tub No. 6 
75 Ibs. technical nitrite of soda 
300 lbs. water 
tub No. 4 


Method.—For diazotization a tub 6 feet in diameter and 6 feet 
deep is used, similar to tub No. 6, Plate F, in dimensions and 
location, but equipped with an agitator to turn at a speed of 
forty revolutions per minute. For dissolving nitrite of soda a 
tub similar to tub No. 4, Plate F, may be used; the outlet and 
pipe feeding to tub No. 6 should be of 2-inch diameter for rapid 
discharge of the nitrite liquor in the diazotization. Seventy-five 
pounds technical nitrite of soda, or one mol. plus 5 per cent ex- 
cess, is dissolved in 300 pounds of water and the solution held in 
readiness for use. A tub 5 feet in diameter and 5 feet deep, 
similar to tub No. 3, Plate F, is used for dissolving the para 


14 Diazo-6. 


82 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


nitraniline hydrochloride; the tub should have a wooden steam 
pipe for heating the acid solution and a large outlet cock with 
channel of 3-inch diameter to facilitate delivery of the para 
nitraniline hydrochloride solution to tub No. 6. 


One hundred and thirty-eight pounds of pure para nitrani- 
line, or an equivalent amount of the 98 per cent powder, is mixed 
to an even paste in a barrel with an equal weight of water and 
230 pounds of muriatic acid. The mixing is to be done on the 
third floor and the paste then dumped into tub No. 3. Water 
is then run into the tub to make the total depth 9 inches and 
solution made by heating to 45° C., for thirty minutes with 
agitation. 

Three hundred pounds of water is now entered in tub No. 6 
by filling to a depth of 2 inches, followed by 500 pounds of 
cracked ice. The solution in tub No. 3 is started flowing down 
onto the cooling mixture, agitation being commenced as soon as 
the ice is well floated. Care should be taken to rinse down any 
residue in tub No. 3. Into the suspension of para nitraniline 
hydrochloride in tub No. 6, 290 pounds of muriatic acid is 
entered, forming a total of 44% mols. of acid for the diazotization, 
and followed by sufficient ice to bring the temperature down to 
7° C., about 1,000 pounds of ice being required. The nitrite of 
soda solution in tub No. 4 is then delivered onto the surface of 
agitating mixture in tub No. 6 by opening the valve in the de- 
livery pipe sufficiently to complete the addition of the nitrite 
liquor in about one and a half minutes. The temperature rises 
to about 10° C., and the nitrite is immediately taken up; no red 
fumes should be noticeable. Agitation is continued for fifteen 
minutes and the diazo then tested for solubility in water. 


The diazo is largely out of solution as prepared. The volume 
of the suspension should be about that of 3,000 pounds of water, 
filling the tub to a depth of 20 inches. A Io cc. sample portion 
should almost entirely dissolve when shaken with 50 cc. of warm 
water. A test for free nitrous acid is of little significance as a 
large excess of sodium nitrite is taken in the method. Intro- 
duction of the nitrite in the manner described above is to be 
preferred to the method of dissolving the nitrite in a barrel and 


DIAZOTIZATION OF THE NITRO ANILINES 83 


turning the nitrite solution into the tub in one addition, as in the 
latter method a certain amount of foaming and loss of nitrous 
acid occurs even with strong agitation. Solution of the para 
nitraniline is most advantageously made at the concentration 
given, using only a portion of the total acid. Further con- 
siderations for obtaining a good result include chiefly attention 
to the details of manipulation, such as insuring an uninterrupted 
flow for the nitrite of soda solution in diazotization, and rinsing 
down the inside walls of tub No. 6 preparatory to and after 
addition of the nitrite. 


A certain small amount of the imino-azo compound is usually 
found present in the diazo. Such formation may be attributed 
to the reactivity of the diazo. Employment of a large propor- 
tion of acid is effective in increasing the speed at which diazoti- 
zation takes place, but, in the present case, can hardly be regarded 
as deterring the formation of the imino-azo compound, as the 
diazo from para nitraniline couples well in an acid condition. 
Ideal conditions in a method are those which bring about com- 
pletion of the reaction in the shortest time practically attainable. 
Such conditions are obtained by efficient distribution of the 
nitrite liquor under rapid agitation. Because of the stability of 
the diazo, the temperature allowable in a practical method is 
of lesser importance, diazotization in water solution at room 
temperature being the practice followed by many operators. 


ALIZARINE YELLOW R*® 


Prepared by coupling diazotized para nitraniline with salicylic 
acid in alkaline solution. 


OH N,Cl 
COONa LASS — pit 
i eae te oe Oars NO »N = N¢ ox 
Po ae 
a ie COONa. 
Sodium salicylate Diazo-6 Alizarine Yellow R 


15 Also known as Alizarine Orange, Mordant Yellow, Orange R, Anthracene 
Yellow, Metachrome Orange, Terra Cotta R, etc. 


84 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Preparation of the Dye.— 
Salicylic Acid, C,H,O,, Molecular Weight = 138. 
Materials.— 


141 lbs. salicylic acid, technically pure 
120 lbs. caustic soda solution, 40° Bé. 
1,500 Ibs. water 


tub No. 2 
350 lbs. soda ash 
500 lbs. ice 
tub No. 8 
1 lb. mol. Diazo-6 
tub No. 6 


15 lbs. ammonium sulfate 


Method.—A tub 9 feet in diameter and 6 feet deep, with an 
agitation to turn at a speed of thirty revolutions per minute (tub 
No. 8, Plate F), is used for the coupling. A tub 5 feet in 
diameter and 5 feet deep (tub No. 2, Plate F), may be used for 
dissolving the component. 


One thousand and five hundred pounds of water is entered in 
tub No. 2 by filling to a depth of 15 inches. One hundred and 
forty-one pounds of technically pure salicylic acid, equal to one 
mol. plus 2 per cent excess, is entered and dissolved by addition 
of caustic soda solution, about 120 pounds of the 40° Be. liquor 
being required. The solution is delivered to tub No. 8 and 350 
pounds of soda ash is added and allowed to dissolve by agitation 
while Diazo-6 is being prepared in tub No. 6 according to the 
method previously given. It is desirable to have the soda ash 
completely in solution before coupling is made. 


When the diazo is ready, 500 pounds of cracked ice is entered 
in tub No. 8 to bring the temperature of the component to 10° C. 
The diazo is then delivered onto the surface of the component 
in a stream adjusted so as to occupy about one hour for the 
addition, the coupling being watched during the addition for ex- 
cessive frothing. After one hour’s agitation the charge is tested 


DIAZOTIZATION OF THE NITRO ANILINES 85 


for absence of the diazo and presence of the component in slight 
excess and then delivered to a blow-case for pressure filtration. 


The final volume of the charge should be that of about 5,000 
pounds of water, and the reaction should be distinctly alkaline 
towards Brilliant Yellow test paper. The dye precipitates volumi- 
nously, so that a fairly thick paste results at the volume stated; 
for this reason addition of the diazo to the component should not 
be hurried or excessive frothing occurs and portions of the 
coupling become acid, shown by a greenish color; ordinarily such 
variations are not met with in the above method, but when a tub 
smaller than No. 8 or with slower agitation is used, or with 
charges larger than one mol., such occurrence should be antici- 
pated. Test for absence of the diazo is made in the usual way 
by spotting a drop of the sample on a filter paper and touching 
the rim of the seepage with a drop of an alkaline solution of 
“R” salt or beta naphthol; the presence of the salicylate is shown 
by spotting and testing the rim of the seepage with a drop of 
ferric chloride solution, a bluish coloration showing positive. 

The dye filters easily and rapidly, a one-molecule charge yield- 
ing somewhat less than two standard pressfuls of a cake con- 
taining about 40 per cent of moisture. The mother liquor con- 
tains but very little dye and no appreciable gain is to be made 
by salting. Before entering in the drying ovens the dye is thor- 
oughly mixed with 15 pounds of ammonium sulfate as a safe- 
guard against ignition during drying and milling. 

The molecular weight of Alizarine Yellow R is 309. The 
marketed product usually contains about 33 per cent of salt. On 
the basis of such reduction, the yield of standard dye theoretically 
possible from a molecule charge would be about 463 pounds. An 
average yield of go per cent of the theory is to be obtained with 
the method during an extended period of production. The dye 
is used on wool with the assistance of a mordant. Production of 
Alizarine Yellow R in the United States during 1920 amounted 
to 83,334 pounds, valued at $0.86 per pound; in 1919 the pro- 
duction was 130,424 pounds, valued at $0.84 per pound. 


86 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


PARA NITRANILINE RED 


Prepared by coupling diazotized para nitraniline with beta 
naphthol in an alkaline condition. 


N,Cl NaS 
Come Ct” 
Eade. Dot oo. NA 

NO, NO, 

Sodium Nitro benzene Para Nitraniline Red 
beta naphtholate diazo chloride 


This dye is insoluble in water and is prepared in the process 
of dyeing and precipitated in the fibers of the material. The 
amount of dye to be prepared at any one time depends upon the 
weight of the material to be dyed and the depth of the shade 
desired. The following procedure may be used for production 
of a medium red shade on 100 pounds of cotton yarn. 

A “mordanting” solution is made by mixing to a paste 2 
pounds of beta naphthol and 2 pounds of caustic soda solution 
of 40° Bé. density, and dissolving in 4 gallons of boiling water. 
For assistance in the “mordanting,” a solution of 2 pounds of 
monopole oil and 2 pounds of aluminum sulfate in 2 gallons of 
water is neutralized by addition of 6 ounces of soda ash and 
added to the naphthol solution, finally making the volume up to 
12 gallons with water. The use of monopole oil and sulfates of 
aluminum facilitates penetration and fixation of the naphthol on 
the yarn. The yarn, made up into bundles of 2 pounds each and 
previously scoured, rinsed and dried, is entered into a tub con- 
taining 6 gallons of the above solution at a temperature of 100° 
F., one bundle being soaked at a time and a pint of the “mordant- 
ing” solution added for each bundle. The mordanted yarn is 
wrung out uniformly and dried in a chamber at 130° F., for 
about four hours, while the diazo solution is being prepared. 

The diazo solution is made by mixing to a paste 24 ounces of 
para nitraniline with 5 pounds of muriatic acid 20° Bé., and dis- 
solving in 5 pints of boiling water. The hot solution is poured 
in a fine stream into 8 gallons of ice water with good stirring and 
a solution of 13 ounces of nitrite of soda in 1 gallon of cold 


DIAZOTIZATION OF THE NITRO ANILINES 87 


water is poured into the para nitraniline hydrochloride, in one 
addition, with very good stirring. The mineral acid in the re- 
sulting diazo solution is neutralized by addition of 1 pound soda 
ash and 24 ounces of acetate of soda dissolved in 1 gallon of 
water. The neutralized diazo solution is filtered through coarse 
muslin and finally made to 12 gallons volume and used without 
delay. 

The mordanted yarn is entered in 2-pound bundles into 6 
gallons of the diazo solution, each bundle being turned twice and 
wrung out well; a pint of the diazo solution is added for each 
bundle of yarn. The dyed yarn is rinsed in cold water, then 
treated in a hot soap solution, rinsed again in cold water and 
dried at 130° F. The shade produced varies with the routine 
followed and depends of course upon whether bleached or un- 
bleached yarn is dyed. Soaping improves the fastness to rubbing; 
prolonged treatment in a very hot soap solution gives a bluer, 
but duller, shade. 

For dyeing the same weight yarn to a deeper shade the quan- 
tities of beta naphthol and para nitraniline would be increased 
in proportion to the depth of the shade desired. For example, 
3 pounds of beta naphthol and 36 ounces of para nitraniline 
would be used to produce a deep red on 100 pounds of yarn, in 
“mordanting”’ and diazo solutions of greater concentration, the 
final volume of each solution being kept at the same total of 12 
gallons and the procedure otherwise similar to that for produc- 
ing the medium shade. 

The use of Para Nitraniline Red on fibers is mainly confined 
to cotton. The dye is also used for coloration of lakes, in which 
case, to permit filtration, the diazo is prepared in solution with 
final volume of 5,000 pounds of water for a one-molecule diazoti- 
zation. ‘The filtered diazo is added to an alkaline solution of 
beta naphthol which contains a suspension of aluminum hydrox- 
ide or barium sulfate to include the precipitated dye. For the 
manufacture of paint materials, a one-molecule charge of the 
dye will suffice for the coloration of about 6,000 pounds of 
barium sulfate. 

7 


88 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Diazotization of Meta Nitraniline.1®°— 
Meta Nitraniline, C,H,O,N., Molecular Weight = 138. 


Metra nitranige Diazo nitro bene chloride 


Materials.— 
276 lbs. meta nitraniline, 100 per cent —= 2 mols. 
460 lbs. muriatic acid, 20° Bé. 
1,300 Ibs. water 


tub No. 3 
3,000 lbs. ice 
575 lbs. muriatic acid 
tub No. 5 
148 lbs. technical nitrite of soda 
400 lbs. water 
tub No. 4 


Method.—A tub 8 feet in diameter and 6 feet deep, fitted with 
an agitator to turn at a speed of thirty revolutions per minute 
(tub No. 5, Plate F), is used for diazotization. The procedure 
to be followed is somewhat analogous to that in preparing 
Diazo-6; for dissolving the amine and the nitrite of soda, tubs 
No, 3 and No. 4 should have the special equipment called for in 
the preparation of Diazo-6. One hundred and forty-eight pounds 
of technical nitrite of soda, or two mols. plus 4 pounds excess, 
is dissolved in 400 pounds of hot water in tub No. 4 and held in 
readiness. 

One thousand three hundred pounds of water is entered in 
tub No. 3 by filling to a depth of 13 inches. Four hundred and 
sixty pounds of muriatic acid is then added and followed by a 
quantity of meta nitraniline equivalent to two mols., or 276 
pounds of the 100 per cent material. Steam is passed into the 
mixture and the temperature maintained at 45° C., for thirty 
minutes, with agitation, to dissolve the meta nitraniline hydro- 
chloride. 


16 Diazo-7, preparation of a two-molecule charge. 


DIAZOTIZATION OF THE NITRO ANILINES 89 


Three thousand pounds of ice is entered in tub No. 5, with the 
agitator stopped, and followed by 575 pounds of muriatic acid. 
The solution in tub No. 3 is then delivered onto the cooling mix- 
ture in tub No. 5, agitation being commenced as soon as the ice 
is well floated. The temperature for diazotization should be 
Y igen OF 

The nitrite of soda solution in tub No. 4 is now delivered onto 
the surface of the agitating mixture in tub No. 5 by opening the 
valve in the 2-inch delivery pipe sufficiently to discharge the 
nitrite liquor in about one and one-half minutes, as in the prepa- 
ration of Diazo-6. The nitrite should be taken up immediately 
and no red fumes should be noticeable; the diazo results mostly 
in solution. Agitation is continued for fifteen minutes and the 
diazo then tested for insoluble matter. 

The final volume of the diazo solution as prepared should be 
about that of 6,000 pounds of water, filling tub No. 5 to a depth 
of 23 inches. A certain small amount of insoluble yellow matter 
is usually found present, as in the diazotization of para nitrani- 
line. Diazotization of meta nitraniline differs from that of para 
nitraniline in that solution of the hydrochloride is more easily 
made and the diazo is more soluble than is the case when para 
nitraniline is being diazotized. In their stability and reactivity 
for coupling the two diazos exhibit similar behavior. 

The grades of commercial meta nitraniline available for manu- 
facturing are not always of the highest purity; frequently tarry 
matter is present as impurity. Such contamination does not seem 
to be disadvantageous to the use of the intermediate in the manu- 
facture of Alizarine Yellow GG, in which meta nitraniline finds 
its greatest use; for any other combination, low grades of the 
nitraniline should be purified by dissolving in muriatic acid, filter- 
ing the solution and reprecipitating with ammonia. 


ALIZARINE YELLOW GG” 


Prepared by coupling diazotized meta nitraniline with salicylic 
acid in alkaline solution. 


17 Mordant Yellow, Anthracene Yellow, Chrome Yellow R. 


go FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


OH N,Cl 
/ \COONa PAS, 
Lia ao |e 

\/NO 


Sodium salicylate Diazo-7 


Preparation of the Dye.— 
Materials.— 


- a 


COONa 
Alizarine Yellow GG 


O; 


285 lbs. 
235 lbs. 
4,000 lbs. 
700 lbs. 


salicylic acid, technicaly pure 
caustic soda solution, 40° Bé. 
water 

soda ash 


tub No. 2 
1,500 lbs. ice 

tub No. 8 

2 Ibs. mol. Diazo-7 


tub No. 5 


25 lbs. ammonium sulfate 


Method.—Tub No. 8 is to be used for the coupling operation, 
and tub No. 2 for dissolving the component, as in the case of 
Alizarine Yellow R. 


Four thousand pounds of water is entered in tub No. 2 by 
filling to a depth of 40 inches. Two hundred and eighty-five 
pounds of technically pure salicylic acid, or two mols. plus 9 
pounds excess, is added and dissolved by addition of sufficient 
caustic soda solution of 40° Bé., density, about 235 pounds being 
required. Seven hundred pounds of soda ash is then slowly 
entered into the solution of the component and allowed to dis- 
solve by agitation for one hour while Diazo-7 is being prepared 
in tub No. 5. The solution of the component is then delivered 
to tub No. 8. 


When the diazo is ready, the temperature of the component 
is brought down to 10° C., by addition of 1,500 pounds of cracked 
ice, and the diazo solution in tub No. 5 is delivered onto the sur- 
face of the component in a stream adjusted so as to complete 
the addition within two hours, the coupling being watched for 


DIAZOTIZATION OF THE NITRO ANILINES OI 


excessive frothing or an acid condition. The charge is agitated for 
an hour after which test is made for presence of the component 
in slight excess and absence of the diazo. The charge is de- 
livered to a blow-case and filtered without delay. 


The final volume should not be greater than that of 13,000 
pounds of water, the charge being easily contained in a standard 
blow-case. The reaction and consistency of the finished charge 
is similar to that stated for Alizarine Yellow R. With care in 
operation and good air pressure, the filtration may be completed 
in three fillings of a standard press such as described in Chapter 
II, a firm, solid cake being obtained with about 30 to 40 per cent 
of moisture. 


The dye is frequently sold as a paste. For this purpose the 
filter cake is shoveled directly into a mixer and diluted with 
water to a strength equal to 20 per cent of the strength of the 
selling standard adopted for the dye on the dry basis. If the dye 
is to be sold as powder, the mixing is confined to addition of 25 
pounds of ammonium sulfate, after which the paste is sent to 
the drying ovens. : 


According to the molecular weight of the dye, 618 pounds con- 
stitutes the yield of pure dye theoretically possible from a two- 
molecule charge. The marketed product, in typical selling 
strengths, contains about 50 per cent of salt, bringing the yield of 
standard dye up to about 1,236 pounds from a two-molecule 
charge. With proper attention to manipulation and prevention 
of mechanical loss of the dye, yields of over go per cent of the 
theory can be obtained for individual charges with the method, 
but for any one dyestuff the average yield obtained during a 
period of production will be found from 5 per cent to Io per 
cent lower than the maximum yield obtainable in test charges, 
decline in the yield being due to occasional losses in charges from 
defects occurring in the equipment and from inexact estimation 
of the proportions of the reacting materials when various grades 
of an intermediate are used. 

Alizarine Yellow GG is used for dyeing wool with assistance 
of a mordant; the shade produced is more yellow than that of 
the R brand. Production for 1920 in the United States amounted 


Q2 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


to 211,580 pounds, valued at $0.63 per pound; in 1919 the pro-. 
duction was 163,170 pounds, valued at $0.72 per pound. 


Ortho nitraniline is of little importance in the azo dye industry, 
the only product of note obtained from this intermediate being 
the Azo Cardinal G, prepared by coupling diazotized ortho 
nitraniline with ethyl benzyl aniline, in acid solution. 


CHAPTERAVIL 


DIAZOTIZATION OF THE SULFONATED ANILINES, AND MANU- 
FACTURE OF THE CHROME YELLOWS AS AND AM, THE 
ORANGES I, II, IIT AND IV, AND METANILE YELLOW 


DIAZOTIZATION OF SULFANILIC ACID* 


Diazotization of Sulfanilic Acid.’*— 
Sulfanilic Acid, C,H,O,NS, Molecular Weight = 173. 


NH, N.—- 
poet ae feces, 
ie Nel 
SO,H SoO,-- 
Sulfanilic acid Anhydride of diazo 
benzene sulfonic acid 
Materials. — 
173 lbs. sulfanilic acid, 100 per cent, == 1 mol. 


120 lbs. caustic soda solution, 40° Bé. 
1,000 lbs. water 
tub No. 2 
250 lbs. muriatic acid, 20° Bé. 
500 Ibs. ice 
tub No. 2 
72 lbs. nitrite of soda, technical 
300 lbs. water 
special container 


Method.—A tub 5 feet in diameter and 5 feet deep, fitted with 
an agitator to turn at a speed of thirty-five revolutions per minute, 
and located on the third floor, such as tub No. 2, Plate F, is to be 
used for the diazotization. 

To prepare the amine, 1,000 pounds of water is entered in 
tub No. 2, by filling to a depth of 10 inches. A quantity of 
technical sulfanilic acid equivalent to 173 pounds of the 100 per 
cent material is then added and followed by 120 pounds of 


_ 18 Diazo-8, a one-molecule preparation, without filtration of the diazo. 


Q4 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


caustic soda solution of 40° Be. density. Steam is passed in and 
the mixture is agitated at 70° C., for thirty minutes. The solu- 
tion made should be definitely alkaline to Brilliant Yellow test 
paper; it is then allowed to stand over night to cool as far as 
possible. 

For the diazotization, 72 pounds of technical nitrite of soda 
is dissolved in 300 pounds of water in a cask or barrel secured 
on a platform or deck on the top of tub No. 2; a spigot fitted in 
the bottom of the cask permits discharge of the solution into tub 
No. 2. Two hundred and fifty pounds of muriatic acid, or two 
mols. plus 20 pounds excess, is entered into the solution of 
sodium sulfanilate in tub No. 2 and followed by sufficient ice to 
bring the temperature down to 8° C.; about 500 pounds of ice 
usually suffices for the cooling. The nitrite of soda solution is 
then delivered, onto the surface of the agitating mixture, in a 
stream adjusted so as to occupy thirty minutes for the addition. 
As the nitrite reacts on the suspended sulfanilic acid, solution 
occurs, but when addition of the nitrite is nearly completed the 
diazo precipitates abundantly. Control of the temperature is of 
importance for prevention of loss of nitrous acid through fuming; 
with good agitation, a final temperature of 20° C., is not detri- 
mental to the result. The diazo results as a white solid suspended 
in the mother liquor and practically insoluble. The final volume 
of the diazo suspension should not be greater than that of 2,500 
pounds of water. Presence of a small amount of muriatic acid 
and free nitrous acid should be shown by tests. As the diazo is 
stable, its use in a coupling may be delayed for almost any 
length of time required by the factory needs. 

Diazo-8 is intended for use in couplings without filtration of 
the diazo. Filtration of the diazo from sulfanilic acid is a prac- 
tical operation for factory purposes, but is much more suitable 
for laboratory work, or operation on a small scale, because of 
the dangerous character of dried traces of the diazo and the me- 
chanical losses incurred in handling a filtered batch in the fac- 
tory, with resultingly lowered yield. A method of preparing the 
filtered diazo is outlined for Diazo-9. 


DIAZOTIZATION OF THE SULFONATED ANILINES 95 


CHROME YELLOW AS 


Prepared by coupling diazotized sulfanilic acid with salicylic 
acid in alkaline solution. 


N.—- OH 

eo 7 \COONa = mr 

moe (NS waso) N=] NCO NOH 

Oe OE Nr Ea ees 

80-41 COONa 

Diazo-8 Sodium Chrome Yellow AS 
salicylate 


Preparation of the Dye.1°— 


Materials.— 
141 lbs. salicylic acid, technical 
120 lbs. caustic soda solution, 40° Bé. 
700 lbs. water 
50 lbs. soda ash 


tub No. 3 
1,000 Ibs. ice 
tub No. 6 
1 lb. mol. Diazo-8 
750 Ibs. salt 
tub No. 2 


Method.—A tub 6 feet in diameter and 6 feet deep, fitted with 
an agitator to turn at a speed of forty revolutions per minute, 
and located on the second floor, such a tub No. 6, Plate F, is to be 
used for the coupling. The component should be dissolved in a 
small tub, such as tub No. 3, and delivered to tub No. 2. Filtra- 
tion is to be made with vacuum, using filter tubs located on the 
first floor. The diazo is first prepared as directed in the preceding 
pages and, before coupling, 750 pounds of salt is added to tub 
No. 2 and dissolved with the diazo. To prepare the component, 
700 pounds of water is entered in tub No. 3 by filling to a depth 
of 7 inches. One hundred and forty-one pounds of technically 
pure salicylic acid, or one mol. plus 2 per cent excess, is added 
and followed by 120 pounds of caustic soda solution, 40° Bé. 


19 Without filtration of the diazo. 


96 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


density. The salicylic acid should dissolve completely upon con- 
tact with the alkali; 50 pounds of soda ash is added and the agi- 
tation continued until a complete solution is obtained. The solu- 
tion of the component is then delivered to tub No. 6. 


For coupling, 500 pounds of ice is entered in tub No. 6 to 
bring the temperature of the component to 0° C. The diazo in 
tub No. 2 is then delivered into the component in a stream ad- 
justed so as to complete the addition within forty-five minutes; 
during coupling 500 pounds of ice should be added to tub No. 6. 
The coupling reaction should be complete almost as soon as the 
diazo has been added, and as soon as a test shows the diazo to 
be completely utilized and the component preseni in a slight ex- 
cess, 750 pounds of salt is added and dissolved and the charge 
is delivered to a suction filter tub. 


The final volume of the charge should be less than that of 
5,000 pounds of water. The dye precipitates in large, flat crystals 
which are bright or dull yellow in color depending upon the ex- 
tent to which the temperature is kept down. The solubility of 
the dye increases rapidly with rising temperature, and to obtain 
a satisfactory yield it is essential that the temperature be kept 
below 5° C., until the charge is filtering. Filtration is retarded 
somewhat by the leaflike form of the crystals, the first layer 
forming a mat which obstructs passage of the mother liquor. 
Filtration of a one-molecule charge can be completed in four 
hours using one standard filter tub, 7 feet in diameter, but it is 
advisable that two such filter tubs be used in order that the fil- 
tration may be completed in an hour and the cake pressed very 
free from the residual liquor. In the present case, as well as in 
the case of other very soluble dyes, it is highly desirable that the 
filter cake contain a minimum amount of moisture, as the drying 
must be conducted at a very low temperature until most of the 
moisture has been removed. 

Chrome Yellow AS has a molecular weight of 366; fairly com- 
petitive selling strengths are those which contain equal parts of 
pure dye and salt. On the basis of such reduction, 732 pounds 
of market ware constitutes the yield theoretically possible from 
a one-molecule charge, provided that the yield is obtained the dye 


DIAZOTIZATION OF THE SULFONATED ANILINES 97 


affords a cheap and profitable chrome yellow. Precautions to be 
observed for obtaining the yield may be summed up as follows: 
Coupling in a cold, well concentrated solution, with addition of 
sufficient salt to equal at least 15 per cent of the weight of the 
charge, and adequate provision for rapid filtration. In small 
charges, such as the one-molecule size, the conditions can be 
achieved without great difficulty; larger charges are difficult to 
conduct with good yield. The method given above represents the 
procedure ordinarily followed; an alternative method is outlined 
below. 
Diazotization of Sulfanilic Acid.?°— 


Materials.— 


180 lbs. sulfanilic acid, 100 per cent 
125 lbs. caustic soda solution, 40° Be. 
1,000 lbs. water 
77 \bs. nitrite of soda, technical 
tub No. 2 
115 lbs. oil of vitriol, 66° Bé. 
1,500 Ibs. ice 
tub No. 6 


Method.—A tub 5 feet in diameter and 5 feet deep, such as No. 
2, is used to dissolve the sulfanilic acid, as in preparation of 
Diazo-8. Diazotization is to be made in a tub such as No. 6, 
with an agitator to turn at a speed of forty revolutions per 
minute. The diazo is to be filtered by vacuum, using a small 
suction filter tub, 5 feet in diameter, located on the first floor. 

One thousand pounds of water is entered in tub No. 2, filling 
to a depth of 10 inches. A quantity of technical sulfanilic acid 
equivalent to 180 pounds of the 100 per cent material, or one mol. 
plus 7 pounds excess, is added and followed by 125 pounds of 
caustic soda solution, 40° Bé. density. Steam is passed in and 
the mixture is agitated at 70° C., for thirty minutes; agitation is 
then continued for two hours to allow some cooling, and 77 
pounds of technical nitrite of soda, or 2 pounds in excess over 
the amount theoretically necessary for the diazotization of the 


29 Diazo-g. 


98 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


quantity of sulfanilic acid taken, is added and dissolved with 
the sulfanilate. 

For diazotization, 1,500 pounds of cracked ice is entered in tub 
No. 6, with the agitator stopped. One hundred and fifteen pounds 
of vitriol, 66° Bé., or slightly more than an equivalence of two 
mols., is added on top of the ice; the solution in tub No. 2 is then 
started flowing down onto the ice and acid mixture in tub No, 6, 
agitation being commenced as soon as the ice is floating. The flow 
of the sulfanilate liquor is adjusted so as to occupy one hour; the 
temperature should be held below 15° C., until addition of the 
sulfanilate is nearly completed, when the temperature may finally 
rise to 20° C. Diazotization should be complete as soon as the 
sulfanilate has been added. The diazo suspension is to be tested 
for presence of free nitrous acid and sulfuric acid, and then de- 
livered to a small suction filter tub, 5 feet in diameter with a bed 
10 inches deep, located on the first floor. Tub No. 6 should be 
rinsed down very slightly with water, and the filtered diazo 
pressed out with a hand float until almost dry. Transfer of the 
diazo from the filter is then made by means of a stout barrel 
capable of holding 55 to 60 gallons. The barrel should have an 
outlet cock of at least I inch inside diameter fitted in the bottom; 
a flat cart is used for carrying the barrel. The diazo paste 
should be removed from the filter by means of a wooden shovel; 
the barrel and contents can then be brought to a tub where coup- 
ling is to be made. 


Preparation of the Dye.— 


Materials.— 
141 lbs. salicylic acid, technical 
120 lbs. caustic soda solution, 40° Bé. 
1,200 lbs. water 
25 lbs. soda ash 
500 lbs. salt 
1,000 lbs. ice 
tub No. 3 
1 charge Diazo-9 
200 lbs. water 
special container 


DIAZOTIZATION OF THE SULFONATED ANILINES 99 


Method.—A tub 5 feet in diameter and 5 feet deep, with an 
agitator to turn at a speed of thirty revolutions per minute, such 
as tub No. 3, Plate F, is to be used for preparation of the com- 
ponent and for the coupling. Filtration is to be made by vacuum, 
using a filter tub located on the second floor. 

In preparation of the component, 1,200 pounds of water is 
entered, by filling to a depth of 12 inches. One hundred and 
forty-one pounds of technically pure salicylic acid is added and 
dissolved with 120 pounds of caustic soda solution; 25 pounds of 
soda ash is then added and dissolved and 500 pounds of salt is 
added and the agitation continued while the diazo is being pre- 
pared. 

Diazo-9 is prepared as directed above and the filtered diazo is 
brought to tub No. 3. The cask containing the diazo is hoisted 
upon the deck of tub No. 3 and 200 pounds of water is mixed 
with the diazo to form a paste thin enough to run evenly. Five 
hundred pounds of cracked ice is added to the component in tub 
No. 3 and the diazo is then delivered into the component in a 
stream adjusted so as to complete the addition within an hour. 
When a test shows the coupling reaction to be completed with 
an excess of the component, 500 pounds of ice is added to chill 
the charge and also act as a diluent and the charge is delivered to 
the suction filter. 

The final volume of the charge is about that of 3,000 pounds 
of water, or two-thirds of the volume attained in the method 
without filtration of the diazo. The employment of a 4 per cent 
excess in the diazo to be filtered should compensate losses in 
handling and from the slight solubility of the diazo so that the 
yield possible from the two methods is similar. Use of a filtered 
diazo allows excellent control of the volume and temperature of 
the coupling so that, with adequate equipment for filtration, the 
method is well adapted for conducting larger charges, of two or 
three molecule size. 


CHROME YELLOW AM 


Prepared by coupling diazotized metanilic acid with salicylic 
acid, in alkaline solution. 


I0O FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Sodium Metanilate, C,H,O,NSNa, Molecular Weight = 195. 
Materials.— 


195 lbs. sodium metanilate, 100 per cent, = 1 mol. 
1,000 Ibs. water 
250 Ibs. muriatic acid, 20° Bé. 
500 lbs. ice 
tub No. 2 
72 lbs. nitrite of soda technical 
300 Ibs. water 
special container 
750 lbs. salt 
141 lbs. salicylic acid, technical 
120 lbs. caustic soda, 40° Bé. 
700 lbs. water 
tub No. 3 
50 lbs. soda ash 
1,000 lbs. ice 
tub No. 6 


Method.—In preparation of this dye, tubs No. 2, 3 and 6 are 
used as in the preparation of the Chrome Yellow AS and filtra- 
tion is made by vacuum. Commercial metanilic acid is to be had 
in the form of its sodium salt, as result of the method of manu- 
facturing this intermediate; the diazo is completely soluble. 

For diazotization, Diazo-10, a quantity of sodium metanilate 
containing 195 pounds of the 100 per cent material is dissolved in 
1,000 pounds of water in tub No. 2; no heat is necessary to bring 
about solution. Seventy-two pounds of nitrite of soda is dissolved 
in 300 pounds of water in a cask located on the deck of tub No. 2. 
Two hundred and fifty pounds of muriatic acid is then added to 
tub No. 2, whereupon the metanilic acid precipitates to a large 
extent, as a flocculent, pinkish mass. The temperature is then 
brought below 8° C:, somewhat less than 500 pounds of ice suf- 
ficing. The nitrite of soda solution is delivered into the metanilic 
acid in a total of thirty minutes’ time. Diazotization is complete 
as soon as the nitrite has been added; presence of excess muriatic 
acid and free nitrous acid should be shown by tests. The diazo 


DIAZOTIZATION OF THE SULFONATED ANILINES IOI 


results entirely in solution, with a final volume of about that of 
2,000 pounds of water. Coupling with salicylic acid is then made 
as in the preparation of the Chrome Yellow AS without filtra- 
tion of the diazo, 750 pounds of salt being entered in the diazo 
solution in tub No. 2 before coupling. The dye has a some- 
what finer shade of yellow than the AS brand but its use is less 
extended because of the higher cost, corresponding to the relative 
prices of metanilic and sulfanilic acids. 


ORANGE I” 


Prepared by coupling diazotized sulfanilic acid with alpha 
naphthol in alkaline solution. 


|, eee ONa  NaSO,¢ FES OH 


Ce+O) = 
Both 


So,-- 
Diazo-9 Sodium Orange I. 
alpha naphtholate 


Preparation of the Dye.— 


Alpha Naphthol, C,,H,O, Molecular Weight = 144. 
Materials.— 
141 lbs. alpha naphthol, refined 
115 lbs. caustic soda solution, 40° Bé. 
700 lbs. water 
15 lbs. soda ash 
tub No. 3 
500 lbs. ice 
1 charge Diazo-9 

200 lbs. water 

special container 
250 lbs. salt 


Method.—A tub 5 feet in diameter and 5 feet deep, with an 
agitator to turn at a speed of thirty revolutions per minute, such 


21 Orange B, S, and R, Naphthol Orange, Tropaeoline G. 


102 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


as tub No. 3, Plate F, is to be used for preparation of the com- 
ponent and for coupling. 

In preparation of the component, 700 pounds of water is 
entered in tub No. 3, filling to a depth of 7 inches. One hundred 
and forty-one pounds of alpha naphthol, 100 per cent, or one mol. 
less 2 per cent, is added and followed by 115 pounds of caustic 
soda solution, 40° Bé. density, and 15 pounds of soda ash. Steam 
is passed in slowly and the mixture is agitated for thirty minutes 
at 60° C. The solution made is then allowed to agitate and cool 
as far as possible while the diazo is being prepared. 


Diazo-9 is prepared from 180 pounds of sulfanilic acid and 
filtered as for the preparation of the Chrome Yellow AS. The 
filtered diazo is transferred in a cask and brought to tub No. 3 
where 200 pounds of water is added and any traces of mineral 
acid remaining in the diazo are neutralized by addition of sufficient 
soda ash. Five hundred pounds of cracked ice is then added to 
the solution of the component in tub No. 3 to bring the tempera- 
ture down to 10° C., and the diazo paste is then delivered into the 
agitating mixture during one hour’s time. Agitation is continued 
for three hours, at the end of which time a test should show 
complete utilization of the component and presence of the diazo 
in excess, the proportions of the reacting materials having been 
calculated with this end in view. Precipitation of the dye is com- 
pleted by addition of about 250 pounds of salt and the charge is 
then delivered to a suction filter. 


The final volume of the charge should be less than that of 
2,000 pounds of water. Use of a filtered diazo is practically 
necessary in preparation of this dye as otherwise a relatively 
large final volume is unavoidable and precipitation of the dye 
with salt is less successful. The excess of the diazo taken is dis- 
charged in the alkaline filtrate in filtration, yielding a product free 
from either of the reacting materials. 


Orange I finds its chief use as one of the permitted dyes em- 
ployed in the coloration of foods. For this purpose purification 
must be made in small batches, involving additional expense and 
loss in yield so that the finished product belongs in a class with 
the fine chemicals. Production of this dye in the United States 


DIAZOTIZATION OF THE SULFONATED ANILINES 103 


during 1920 amounted to 14,684 pounds, valued at an average 
price of $5.18 per pound. The price is the highest recorded for 
any azo dye produced in quantity in that year. Actual cost to 
produce the crude dye may be stated at slightly less than $1.00. 


ORANGE III” 


Prepared by coupling diazotized sulfanilic acid with dimethyl 
aniline in acid solution and precipitating the dye in alkaline solu- 
tion. 


CH, CH, 


es 4 
| Le Noli OS 
\ ) ‘ aN 3 -- NaSO< YN =NC_ N(CH), 


Orange III 
ieee 9 Dimethyl 
aniline 


Preparation of the Dye.— 
Dimethyl Aniline, C,H,,N, Molecular Wieleit. 1121. 
Materials.— 
180 lbs. sulfanilic acid, 100 per cent 
125 lbs. caustic soda solution, 40° Bé. 
1,000 lbs. water 
77 \bs. nitrite of soda, technical 


tub No. 2 
160 Ibs. oil of vitriol, 66° Bé. 
1,500 lbs. ice 
tub No. 6 
3 Ibs. bisulfite of soda 
750 lbs. salt 
121 lbs. dimethyl aniline = 1 mol. 
500 lbs. ice 
tub No. 6 


22 Helianthin, Methyl Orange, Gold Orange MP. 
8 


I04 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


250 lbs. caustic soda solution, 40° Bé. 
500 lbs. water 
tub No. 4 
15 lbs. ammonium sulfate 


Method.—A tub 6 feet in diameter and 6 feet deep, with an 
agitator to turn at a speed of forty revolutions per minute, such 
as tub No. 6, Plate F, is to be used for diazotization and coupling. 
Filtration is to be made by vacuum, using a suction filter tub 
located on the first floor. A small tub, such as the nitrite dissolv- 
ing tub No. 4, is used to hold a solution of caustic soda. 

One hundred and eighty pounds of sulfanilic acid is to be 
diazotized according to the directions given for preparation of 
Diazo-9, but no filtration of the diazo is to be made. The excess 
nitrous acid present in the diazo is to be destroyed as follows: 
Three pounds of bisulfite of soda is dissolved in 30 pounds of 
water and portions of the bisulfite liquor added to the diazo sus- 
pension in tub No. 6 until a drop of the diazo leaves starch potas- 
sium iodide paper white; no excess of bisulfite is to be used. 
Seven hundred and fifty pounds of salt is then added to the diazo 
and allowed to dissolve. 

Five hundred pounds of water is entered in the small tub No. 
4 by filling to a depth of 13 inches; 250 pounds of caustic soda 
solution, 40° Bé. density is added and the mixture stirred until 
even. One hundred and twenty-one pounds of dimethyl aniline 
is added to the diazo in tub No. 6. The diluted caustic soda 
solution in tub No. 4 is then delivered into tub No. 6 in a fine 
stream, taking two hours to complete the addition and holding 
the temperature below 15° C., by addition of ice, about 500 
pounds being required. The amount of caustic soda taken should 
leave the charge strongly alkaline; no odor of dimethyl aniline 
should be noticeable in the finished charge. The completeness of 
the precipitation should be tested but the amount of salt previ- 
ously added ordinarily will suffice for the volume attained in the 
present charge. Fifteen pounds of ammonium sulfate is finally 
added and allowed to dissolve, to decompose the excess of caustic 


DIAZOTIZATION OF THE SULFONATED ANILINES 105 


soda, and after thirty minutes’ agitation the charge is delivered to 
a suction filter tub. 

For preparation of Orange III as the ammonium salt of the 
dye compound, 300 pounds of the 26 per cent ammonium hy- 
droxide is to be substituted for the caustic soda used in the above 
preparation and the drying then conducted at a temperature be- 
low 50° C. 

For another method of preparing Orange III reference is made 
to the chapter on experimental plant work.—Chapter XIII. 


ORANGE II 


Prepared by coupling diazotized sulfanilic acid with beta naph- 
thol in alkaline solution. 


N.—-v N === N 
ONa yes YarOH. 
0 SOLOS 
| es 
se UO ee ,Na 
Sodium Diazo-11 Orange II 


beta naphtholate 
Preparation of the Dye.?°— 


Maiterials.— 
Price per 1b., 
Dollars Cost 
720 lbs. beta naphthol, technical 0.24 $172.80 
575 lbs. caustic soda solution, 40° Bé. 0.01% 7.18 
50 lbs. soda ash 0.02 1.00 
3,000 lbs. water 
evtubs Noes 
865 lbs. sulfanilic acid, 100 per cent, 
Sanceiols: 0.24 207.60 
600 lbs. caustic soda solution, 40° Beé. 0.01% 7.50 
3,000 lbs. water 
tub No. 2 
365 lbs. nitrite of soda, technical 0.09 32.85 
750 lbs. water 
tub No. 1 


23 Preparation of Orange II in five-molecule charges. 


106 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Price per Ib. 


Dollars __ Cost 

525 lbs. oil of vitriol, 66° Bé. 0.0034. 3.93 

4,500 Ibs. ice $6.00 per ton 13.50 

50 lbs. soda ash 0.02 1.00 

500 lbs. salt 0.0034 B75 
tub No. 5 

2,500 lbs. ice 7.50 
tub No. 7 

Total cost $458.61 


Method.—The location and dimensions of tubs No. I, 2, 3, 5 
and 7, used in this preparation, are according to Plate F. Diazo- 
tization is to be conducted in tub No. 5, followed by coupling in 
tub No. 7, and filtration by pressure. The solutions of beta naph- 
thol, sodium sulfanilate, and nitrite of soda, are to be prepared 
in the order mentioned, in tubs No. 3, 2 and 1. 

Solution of the Component: ‘Three thousand pounds of water 
is entered in tub No. 3, filling to a depth of 30 inches. Seven 
hundred and twenty pounds of technical beta naphthol, equivalent 
to somewhat less than five mols. of the 100 per cent material, is 
added and followed by 575 pounds of caustic soda solution and 
50 pounds of soda ash. Steam is passed in slowly to bring the 
temperature to 65° C., and the mixture is agitated at that tem- 
perature for thirty minutes to insure solution and then allowed 
to cool under agitation. 

Solution of the Amine: Three thousand pounds of water is 
entered in tub No. 2, filling to a depth of 30 inches. A quantity 
‘of technical sulfanilic acid equivalent to 865 pounds of the 100 
per cent material, or five mols., is added and followed by 600 
pounds of caustic soda solution. Steam is passed in and the 
batch is agitated at 75° C., for thirty minutes, to bring about solu- 
tion. If the intermediate is available in the form of its sodium 
salt, the operation is confined to dissolving 975 pounds of the 
100 per cent material, or five mols., in 3,000 pounds of water. 

Solution of the Nitrite: Seven hundred and fifty pounds of 
water is entered in tub No. 1, filling to a depth of 20 inches; 
steam is passed in to heat the water to 85° C., and 365 pounds of 


DIAZOTIZATION OF THE SULFONATED ANILINES 107 


technical nitrite of soda, or five mols. plus 5 pounds excess, is 
added and dissolved by stirring with a paddle. Solution of the 
nitrite brings the temperature down to about 35° C. 


Preparation of Diazo-11: Four thousand five hundred pounds 
of cracked ice is entered in tub No. 5, with the agitator stopped. 
Five hundred and twenty-five pounds of vitriol, 66° Bé., or ten 
mols. plus 25 pounds excess, is drawn from the storage tank 
and entered in tub No. 5 on top of the ice. The solution of 
sodium sulfanilate in tub No. 2 is now delivered into the cooling 
mixture in tub No. 5 and agitation commenced as soon as the 
ice is floating. The initial temperature for diazotization should 
be 8° C., or below. The nitrite of soda solution in tub No. 1 is 
delivered onto the surface of the agitating mixture in tub No. 
5 in a stream adjusted so as to complete the flow in one hour. 
During diazotization the temperature may gradually rise to 20° 
C. without harm to the result but quick rises in temperature must 
be prevented by controlling the flow of the nitrite liquor, or loss 
of nitrous acid from fuming results. The nitrite should be 
rapidly taken up and no red fumes noticeable under agitation of 
the character rendered in tub No. 5. Diazotization is complete 
as soon as the nitrite solution has all been added; the diazo 
should be acid to Congo Red test paper and show the presence 
of free nitrous acid in excess. Before coupling, the free mineral 
acid is to be neutralized completely by gradually adding small 
amounts of soda ash until a test shows mineral acid to be absent. 
Five hundred pounds of salt is then added and allowed to dis- 
solve. The final volume of the diazo should be that of about 
10,000 pounds of water, filling the tub to a depth of about 4o 
inches, 

Coupling: While the diazo is being prepared, the solution of 
beta naphthol in tub No. 3 is delivered to the large tub No. 7 
Two thousand, five hundred pounds of cracked ice is added in 
tub No. 7 to bring the temperature of the component to 10° C., 
for coupling . The diazo is then delivered onto the surface of the 
agitating component in tub No. 7, the flow of the diazo being ad- 
justed so as to be completed in two hours: the crystalline residue 
in tub No. 5 is rinsed down into the coupling. The dye pre- 


108 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


cipitates on formation, in flat thick crystals, and is very little 
soluble under the conditions; no frothing should occur in the 
charge during coupling. The progress of the reaction is tested, 
and agitation continued over night; on the following day the 
charge is delivered to a blow-case for pressure filtration. 


The final volume of the charge is equivalent to that of about 
18,000 pounds of water. This volume is greater than the capacity 
of a standard blow-case and it is necessary to deliver two-thirds 
of the charge to the blow-case and commence filtration, the re- 
mainder of the charge being added to the blow-case as soon as 
the first pressfuls of the dye have been dumped; for a daily 
routine charge, two standard filter presses should be available. 
The dye filters only moderately fast, the crystals matting to some 
extent and hindering passage of the filtrate. With air pressure 
of from 40 to 45 pounds per square inch, a cake containing about 
40 per cent of moisture is obtained. 


The proportions of the diazo and component taken in the 
method are such that with accurate weighing of the sulfanilic 
acid and beta naphthol a slight excess of the diazo results in the 
charge. If any uncertainty should exist regarding the percentage 
composition of the sulfanilic acid available, a calculated excess of 
2 per cent should be taken to insure presence of the diazo in ex- 
cess and completion utilization of the component. Free beta 
naphthol is detrimental to filtration and to the dyeing quality of 
the product. 


Manufacture of Orange II exhibits fewer drawbacks than that 
of perhaps any dye in the azo class. The intermediates are to 
be had in a well standardized degree of purity, the diazo is stable, 
and coupling takes place rapidly; the dye is very little soluble in 
the mother liquor and filters and dries well; with care in manipu- 
lation a yield of 95 per cent of the amount theoretically possible 
is obtained. The work of dissolving the materials and delivering 
the solutions to successive tubs may be allotted to one man, with 
assistance given for icing. With a daily charge commenced at 
7 A. M., union of the diazo and component can be made at 
1 P. M., at which time the previous day’s charge will be out of 
the coupling tub. 


DIAZOTIZATION OF THE SULFONATED ANILINES IOQ 


The molecular weight of Orange II is 350. For selling pur- 
poses, the factory product is reduced only to a slight degree 
necessary to maintain uniformity in the output, so that reputable 
market wares contain as high as 80 per cent pure dye; with a 
selling standard of this strength, the yield of saleable dye the- 
oretically possible from the present charge amounts to about 
2,150 pounds, a yield of 2,000 pounds of dye being ordinarily ob- 
tained. At the present time, 1922, the cost of materials used in 
such a charge totals $458.61; the manufacturing expense varies 
of course with the volume and success of the production but may 
be stated at an average of 11 cents per pound of finished dye, 
to cover cost of labor and the accessories to production; the costs 
may be compared with a value of 40 cents per pound for the 
product and an average yield of 2,000 pounds of dye. 

Orange II is used for wool and silk in acid bath and is the 
basis of many mixed dyes and dyeing combinations; it dyes 
easily level, with excellent fastness towards most treatments, 
but the fastness towards washing and milling treatment is not so 
marked. The production in the United States in 1920 substan- 
tiates the claim made for it as the most important orange, total- 
ing 1,859,341 pounds, valued at $0.62 per pound. For the azo 
dyes this quantity of production is surpassed by only a few of 
the blacks. 


METANILE YELLOW 


Prepared by coupling diazotized metanilic acid with diphenyl- 
amine in an acid condition and completing the dye in alkaline 
solution. 


NH — 
ee aes 
e- ay erly eeee 


Diazo-12 Diphenylamine Metanile Yellow 


IIo FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Preparation of the Dye.?*— 


Diphenylamine, C,,H,,N, Molecular Weight = 169. 
Materials.— 
600 lbs. sodium metanilate, 100 per cent 


3,000 Ibs. 
225 lbs. 


450 lbs. 
3,000 Ibs. 


5 Ibs. 


750 Ibs. 


1,000 Ibs. 
250 lbs. 


495 lbs. 


3,000 Ibs. 


3,000 Ibs. 
750 Ibs. 


200 lbs. 
1,500 Ibs. 


water 
nitrite of soda, technical 


oil of vitriol, 66° Beé. 
ice 


bisulfite of soda 

ice 

oil of vitriol, 66° Bé. 
acetic acid, 56 per cent 


diphenylamine, = 3 mols. 


ice 


water 
salt 


soda ash 
water 


tub No. 2 


tub No. 5 


special container 


tub No. 5 


tub No. 8 


tub No. 3 


Method.—The location and dimensions of tubs No. 2, 3, 5 and 


8 used in this preparation are according to Plate F. Diazotiza- 
tion and coupling are to be conducted in tub No. 5. The acid 
coupling is to be filtered on suction tubs located on the first floor 
and transferred to tub No. 8 for neutralization and then filtered 
by pressure. A special tub or container, 5 feet in diameter 
and 5 feet deep, is to be located above the deck of tub No. 
5. This tub should be lead-lined throughout, including the out- 
let, and be fitted with a lead-covered agitator to turn at a speed 
of twenty revolutions per minute; for heating the diphenyl- 
amine mixture, a steam coil should be provided, consisting of a 


24 Preparation of Metanile Yellow in three-molecule charges. 


DIAZOTIZATION OF THE SULFONATED ANILINES EI 


single turn of 1-inch lead pipe secured on the bottom of the tub. 
The outlet should discharge directly into tub No. 5 through a 
2-inch channel and the plug cock should be well coated with 
graphite grease to prevent sticking. 


Solution of the Amine: Three thousand pounds of water is 
entered in tub No. 2, filling to a depth of 30 inches. A quantity 
of sodium metanilate equal to 600 pounds of the I00 per cent 
material, or three mols. plus 15 pounds excess, calculated on 
the molecular weight of 195, is added and dissolved by agitation 
for one hour. When solution of the metanilate is complete, 225 
pounds of technical nitrite of soda, or 3 pounds excess over the 
amount theoretically necessary, is added and dissolved with the 
metanilate. | 


Preparation of Diazo-12: Three thousand pounds of cracked 
ice is entered in tub No. 5 with the agitator stopped, and followed 
by 450 pounds of vitriol, 66° Bé. The solution in tub No. 2 is de- 
livered into tub No. 5, taking one hour for the addition, agita- 
tion being commenced as soon as the ice is floating; the tem- 
perature should be held below 12° C., during diazotization, to 
hold the charge well in control, but may rise gradually to 20° 
C. toward the end without harm provided that no fuming of 
nitrous acid occurs. The excess nitrous acid in the resulting 
diazo solution is to be destroyed by adding portions of a solution 
made from 5 pounds of bisulfite of soda and 50 pounds of water 
until a starch potassium iodide paper is left white when treated 
with a drop of the diazo; no excess of bisulfite should be used. 
The final volume of the diazo should be about that of 7,000 
pounds of water, filling the tub to a depth of 27 inches. 


Preparation of the Component: While the diazo is being pre- 
pared, the component is made up in the lead-lined tub as follows: 
Seven hundred and fifty pounds of cracked ice is entered, with 
precaution not to damage the lead work of the tub; 1,000 pounds 
of vitriol, 66° Bé., is added very slowly; agitation is commenced 
and 250 pounds of acetic acid, 56 per cent, is added and followed 
by 495 pounds, or three mols., of diphenylamine. The tem- 
perature is maintained at 65° C., by passing steam through the 
lead pipe coil in the bottom of the tub. The resulting solution of 


II2 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


diphenylamine is to be used without delay and its preparation 
should be timed so as to finish simultaneously with that of the 
diazo. 

Coupling: When the component is ready, the temperature of 
the diazo is brought to 5° C., or below, by addition of 1,500 
pounds of ice. The outlet of the lead-lined tub is opened and 
the solution of the component is delivered into the diazo in a 
stream adjusted so as to complete the addition in one hour. The 
flow is halted periodically for addition of more ice, up to 1,500 
pounds, to maintain the low temperature and precipitate the com- 
ponent in a fine state of division. The lead-lined tub is finally 
washed down with a mixture of 200 pounds of water and 25 
pounds of vitriol heated to 65° C. The sides of the coupling tub 
are to be rinsed down and agitation then continued for forty- 
eight hours to completely utilize the diphenylamine. 


The volume of the coupling should be about that of 13,000 
pounds of water, filling the tub to a depth of 50 inches. When 
a test shows the coupling reaction to be completed, the charge is 
delivered to two suction filter tubs located on the first floor; 
when the mother liquor is discharged, the cake should be washed 
twice from a shower arranged over the tubs and finally pressed 
out with a hand float; filtration usually proceeds rapidly. 


Neutralization: Three thousand pounds of water is entered 
in tub No. 8 by filling to a depth of 9 inches and 500 pounds of 
salt is added and dissolved. The cake is transferred from the 
filters to tub No. 9, and a solution of 200 pounds of soda ash in 
1,500 pounds of water, made up in tub No. 3, is delivered into 
tub No. 9 very slowly, to avoid frothing over. The alkaline 
charge is warmed to 45° for an hour, formation of the sodium 
salt being completed only slowly. Sufficient salt is added to com- 
pletely precipitate the dye, about 250 pounds in addition to the 
salt previously entered usually sufficing. The charge is allowed 
to cool by agitation over night and on the following day is de- 
livered to a blow-case for pressure filtration. The filtration pro- 
ceeds only moderately fast but offers no difficulty ; the press cake 
obtained is fairly high in moisture and drying must be com- 
menced at a temperature below 50° C. 


DIAZOTIZATION OF THE SULFONATED ANILINES 113 


In conducting the coupling operation it is essential that the com- 
ponent be completely utilized; free diphenylamine is an insoluble 
and undesirable constituent for the finished dye. To this end 
the volume of the coupling mixture should not be increased un- 
necessarily ; with an excess of the diazo and a good state of divi- 
sion in the component, coupling of a concentrated, strongly acid 
mixture is to be completed in from thirty-six to forty-eight hours. 
The presence or absence of diphenylamine may be tested by 
filtering a portion of the charge and warming the precipitate 
with dilute sodium carbonate solution, when, in a completed 
coupling, there should be positively no odor of diphenylamine. 
Should the diazo be consumed and the component left in excess, 
a quantitative determination of the excess must be made and a 
suitable amount of metanilic acid diazotized and added to the 
charge, agitation being then continued until the reaction is com- 
pleted. 


The factory product resulting from the above described method 
of finishing contains a high percentage of salt and serves for 
preparation of the “ordinary,” or single strength market wares, 
which contain about two parts of pure dye and one part salt. 
The molecular weight of Metanile Yellow is 375, and on the 
basis of the single strength reduction a yield of 1,731 pounds of 
market dye is theoretically possible from a three-molecule charge. 
For finishing the dye to obtain the “Extra,” or double strength, 
a highly concentrated ware containing about nine parts of pure 
_ dye and one part of salt, neutralization of the acid coupling must 
be conducted in water without addition of salt and precipitation 
of the dye effected by adding a large proportion of ice, the ice 
acting as a cooling agent and diluent to remove sodium sulfate; 
the dye is very little soluble below 5° C., but as the final volume 
is fairly large a lowered yield results. 


The aggregate cost of materials consumed in a three-molecule 
charge, with sodium metanilate valued at 74 cents per pound 
and diphenylamine at 56 cents, totals about $800, to which must 
be added a manufacturing cost of 11 cents per pound. The yield 
of single strength dye should average over 1,500 pounds per 
charge, valued at 80 cents per pound at the lowest present quo- 


II4 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


tations. Two charges per week may be carried with the method 
and will ordinarily satisfy the demands upon one factory. The 
dye is used in acid bath for wool and silk and is applied for paper 
and for jetting of black dyes. Production of the dye in the 
United States during 1920 totaled 629,437 pounds valued at 
$1.64 per pound. The trend of prices for dyes is noticeable in 
the average price of $1.20 for Metanile Yellow in 1921 and 
market quotations of 80 cents to $1.20 for the dye in 1922. 


ORANGE IV* 


Prepared by coupling diazotized sulfanilic acid with dipheny]l- 
amine in the acid condition and completion of the dye in alkaline 
solution. 


“i 
Z0-9 Diphenylamine Orange IV 


Preparation of the Dye.— 


Materials.— 

300 Ibs. ice 

400 lbs. oil of vitriol, 66° Bé. 

100 lbs. acetic acid, 56 per cent 

169 lbs. diphenylamine, = one mol. 

special container 

1 charge, Diazo-9 
3 Ibs. bisulfite of soda — 


tub No. 6 
200 lbs. soda ash 
1,500 lbs. water 
1,500 lbs. ice 
tub No. 6 


2 New Yellow, Acid Yellow. 


DIAZOTIZATION OF THE SULFONATED ANILINES II5 


Method.—A tub 6 feet in diameter and 6 feet deep, fitted with 
an agitator to turn at a speed of forty revolutions per minute, 
such as tub No. 6, Plate F, is to be used for the diazotization, 
coupling and neutralization. Filtration is to be made by vacuum, 
using a suction filter tub located on the first floor. For prepara- 
tion of the component, a lead-lined tub similar to that described 
for use in the preparation of Metanile Yellow, is to be located 
above the deck of tub No. 6. 


The diazo is to be prepared from 180 pounds of sulfanilic 
acid, 100 per cent, according to the directions given for the prep- 
aration of Diazo-9 earlier in the chapter; the diazo is not to be 
filtered; the excess nitrous acid is to be destroyed by addition of 
a 10 per cent solution of sodium bisulfite. 


The component is made up in the lead-lined container by 
entering 300 pounds of ice, 4oo pounds of vitriol, 100 pounds of 
acetic acid and 169 pounds of diphenylamine, in the order men- 
tioned, and agitating at 65° C., until used. The temperature of 
the diazo in tub No. 6 is then brought down to 5° C., or below 
and the solution of the component delivered into tub No. 6 taking 
thirty minutes for the addition, and holding the temperature be- 
low 5° C., by addition of 500 pounds of ice, finally rinsing down 
the lead-lined tub with a mixture of 10 pounds of vitriol and 
100 pounds of water, heated to 65° C. The charge is agitated for 
forty-eight hours and the completion of the coupling reaction 
recognized as in the case of Metanile Yellow. When the di- 
phenylamine has been completely utilized the charge is delivered 
to a suction filter tub and after filtration is washed twice with 
water and pressed out with a hand float. 


For the completion, 1,500 pounds of water is entered in tub 
No. 6, filling to a depth of 10 inches, and 200 pounds of soda 
ash is added and dissolved. The filtered acid coupling is trans- 
ferred from the filter to tub No. 6 and steam is passed in to heat 
the charge to 45° C., to insure formation of the sodium salt. 
The charge may be allowed to agitate until the following day 
and cool to room temperature, when the dye will be found to 
have precipitated completely, or, the warm charge may be cooled 
to 5° C., by addition of sufficient ice and filtered immediately, 


116 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


by vacuum. In contrast to Metanile Yellow, Orange IV filters 
very rapidly, yielding a cake low in moisture, and is dried with 
comparative ease. 

Orange IV is used similarly to Metanile Yellow, but the shade 
produced is of a stronger cast; for a given quantity of wool, 
two parts of pure Orange IV produce a shade of the same depth 
as that of three parts of pure Metanile Yellow. For the market, 
Orange IV is only slightly reduced, so that a brand such as New 
Yellow Extra contains about nine parts of pure dye and one part 
of salt, but is much stronger than a Metanile Yellow Extra con- 
centrated. 


Some objection to Orange IV is to be met on the ground of 
insolubility of the sodium salt, but such objection is hardly 
justified as the pure sodium salt is easily soluble in hot water at 
the concentrations employed for dyeing, and it may be considered 
that earlier in the history of the dye free diphenylamine present 
in market wares gave rise to the popular impression. A more 
cogent objection to the sodium salt, from a selling point of view, — 
would lie in the unattractive color, a pale, more or less dingy 
orange or tan; for this reason, employment of the highly soluble 
and richly colored potassium salt may be desirable although not 
imperative. No difference between the two salts is noticeable in 
the depth or quality of the shade produced. 


CHARTER VITk 


DIAZOTIZATIONS OF ACETYL PARA PHENYLENE DIAMINE AND 
ANTHRANILIC ACID, AND MANUFACTURE OF AMINO 
NAPHTHOL RED B, AZO CORALLINE, AND 
ACID ANTHRACENE RED B 


Diazotization of Acetyl Para Phenylene Diamine.?°— 
Acetyl Para Beenylene Diamine, C,H,,ON,, 
Molecular Weight = 150. 


CH,CONH CH,CONH 
| bs) 
\/ 
NH, N,Cl 
Acetyl para Acetylamino diazo benzene 


phenylene diamine 


Acetyl para phenylene diamine is frequently manufactured in 
the factory where used. In such case, to avoid the cost and in- 
convenience of isolating the solid form of the intermediate, the 
technical solution which is obtained in its manufacture is used 
directly for diazotization. The solution will hold at a concen- 
tration of 3 per cent without crystallizing at ordinary tempera- 
ture, and can be employed at such dilution with satisfactory re- 
sults. Diazo-13 takes up the diazotization in dilute solution, and 
Diazo-14 the diazotization when the material is available in the 
solid form. 

Materials.—Diazo-13. 

150 lbs. acetyl para phenylene diamine, = one mol., in 
the form of a 3 per cent solution. 
3,500 lbs. ice 


tub No. 5 
345 lbs. muriatic acid, 20° Bé. 
640 Ibs. water 
tub No. 2 
75 lbs. nitrate of soda, technical 
300 Ibs. water 
, tub No. 1 


26 Diazo-13 and 14. 


118 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Method.—A tub 8 feet in diameter and 6 feet deep, with an 
agitator to turn at a speed of thirty revolutions per minute, such 
as tub No. 5, Plate F, is used for preparation of the amine and 
diazotization. A wooden pipe should be provided in tub No. 5, 
for conducting the solution of nitrite of soda to the bottom of 
the tub during diazotization. Small tubs, such as No. 1 and No. 
2, Plate F, are to be used for preparing solutions of nitrite of 
soda and muriatic acid. 


A calculated quantity of acetyl para phenylene diamine solu- 
tion, containing 150 pounds of the 100 per cent material, is 
pumped into tub No. 5 from storage. Measurement of the solu- 
tion may be made either by volume or by weight and the exact 
percentage content of the diamine solution must be known, to- 
gether with the exact diameter of the tub. In the case of a 3.00 
per cent solution in a tub 8 feet in diameter, the requisite 5,000 
pounds of solution fills the tub to a depth of 19.3 inches, an 
allowance of I per cent being made for the displacement due to 
the agitator. Measurement by actual weighing of such a dilute 
solution is less practical. 


Seventy-five pounds of technical nitrite of soda or one mol. 
plus 5 per cent excess is dissolved in 300 pounds of water in 
tub No. 1, and 345 pounds of muriatic acid, or three mols., is 
diluted to a total of 1,000 pounds by entering into tub No. 2 and 
adding water to a depth of 10 inches. Two thousand and five 
hundred pounds of cracked ice is entered in tub No. 5 to bring 
the temperature below 2° C., and the solution of muriatic acid 
in tub No. 2 is delivered into the agitating mixture in tub No. 5. 
Diazotization is then made by delivering the nitrite of soda solu- 
tion under the surface of the diamine, the flow of the nitrite 
being adjusted so as to complete in fifteen minutes; agitation is 
continued for fifteen minutes after entering the nitrite, and the 
diazotization may then be considered complete. One thousand 
pounds of ice is added to hold the temperature below 5° C.. 
until the diazo solution is used in coupling. 

The volume of the diazo should not be greater than that of 
about 10,000 pounds of water, filling the tub to a depth of 38 
inches. The solution should of course show presence of muriatic 


DIAZOTIZATION OF ACETYL PARA PHENYLENE DIAMINE IIQ 


and nitrous acids in excess but no specific test is available to 
show completeness of diazotization. In concentrated solution 
the proportion of muriatic acid sufficing for diazotization of 
acetyl para phenylene diamine is only slightly over two mols.; 
with the considerable dilution in the present case three mols. 
should be taken to insure rapid diazotization. Muriatic acid 
should be entered only after dilution, into a cold and well agitated 
solution, to avoid the possibility of hydrolyzing the acetylamino 
group; a heavy froth on the diazo indicates that some hydrolysis 
has taken place. 


Materials.—Diazo-1 4. 
1,000 lbs. water 
250 lbs. muriatic acid, 20° Bé. 
2,500 lbs. ice 
150 lbs. acetyl para phenylene diamine, 100 per cent, in 


solid form , 
tub No. 6 
72 Ibs. nitrite of soda, technical 
300 lbs. water 
tub No. 4 


Method.—A tub 6 feet in diameter and 6 feet deep, with an 
agitator to turn at a speed of thirty revolutions per minute, such 
as tub No. 6, Plate F, is used for the diazotization. 


One thousand pounds of water is entered in tub No. 6 by 
filling to a depth of 7 inches. Two thousand pounds of cracked 
ice is added and followed by 250 pounds of muriatic acid, or 
two mols. plus 20 pounds. Agitation is commenced as soon as the 
ice is floating and a quantity of acetyl para phenylene diamine 
crystals equivalent to 150 pounds of the 100 per cent material is 
entered. A solution of 72 pounds of technical nitrite of soda, 
made up in tub No. 4, is now delivered into tub No. 6 in a 
stream adjusted so as to complete the addition in thirty minutes. 
Agitation is continued for fifteen minutes after the nitrite solu- 
tion has been added and the diazo is then tested for the presence 
of free nitrous acid and muriatic acid. Five hundred pounds of 

9 


120 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


ice is added to hold the temperature below 5° C., until the diazo 
is used in coupling. 

The use of pure solid acetyl para phenylene diamine for the 
manufacture of dyes is practical only in special cases, such as 
those where the mono azo dyes prepared from this intermediate 
are to be used for manufacture of corresponding disazo dyes. 
For the mono azo dyes, the advantages to be obtained from the 
smaller final volume of Diazo-14, as compared with Diazo-13, 
are largely offset by the difference in cost of the materials, the 
1920 valuation for solid acetyl para phenylene diamine averaging 
$1.63 per pound while in the same year the material could be 
produced and used in solution at a cost of less than go cents per 
pound. Costs for 1922 offer about the same ratio, the solid being 
quoted at prices ranging from $1.20 to $1.40 per pound and cost 
to produce the intermediate without isolation from solution hold- 
ing at about 75 cents per pound. 


AMINO NAPHTHOL RED B” 


Prepared by coupling diazotized acetyl para phenylene diamine 
with the acetylated acid “H,” in alkaline solution. 


CH,CONH HO NHCOCH, 
Von _ 
NaSO, SO,Na 
N,Cl Acetyl ‘‘H”’ acid 
Diazo-13 disodium salt 


HO NHCOCH 
CH,CONHE > = Ne 


saa ioe 
NaSO,;\ 4\/S0,;Na 
Amino Naphthol Red B 


Preparation of the Dye.— 

Preparation of the dye includes the acetylation of “H” acid 
to form the component. For a detailed method of acetylation 
reference is made to the preparation of Amino Naphthol Red G, 
in Chapter IV. 


27 Azo Fuchsine B. 


DIAZOTIZATION OF ACETYL PARA PHENYLENE DIAMINE I2I 


Materials.— 


348 Ibs. “H” acid disodium salt, 100 per cent 
120 lbs. caustic soda solution, 40° Bé.. 
750 lbs. water 
500 lbs. ice 
175 lbs. acetic anhydride, 100 per cent 
150 lbs. soda ash 


tub No. 3 
I lb. mol. Diazo-13 
tub No. 5 
250 lbs. soda ash 
500 Ibs. salt 
2,500 lbs. ice 
tub No. 7 


Method.—The dimensions and locations of tubs No. 3, 5 and 
7 for this preparation are according to Plate F. | 

A quantity of “H” acid paste or powder containing 348 pounds 
of the 100 per cent material, or one mol. plus 2 per cent excess, 
is to be acetylated in tub No. 3 and the acetylated mixture then 
neutralized by adding very carefully 150 pounds of soda ash. 
The solution of the component is then delivered to the large tub 
No. 7, for coupling, and 250 pounds of soda ash and 500 pounds 
of salt are added and the mixture agitated while Diazo-13 is 
being prepared in tub No. 5. 

When the diazo is prepared, 2,500 pounds of cracked ice is 
entered in tub No. 7 to insure a temperature very close to 0° C., 
for coupling. The diazo solution is then delivered onto the sur- 
face of the component in a stream adjusted so as to complete 
the addition in an hour; the charge must be watched for exces- 
sive frothing during the addition. Agitation is continued until 
the following day when the dye will be found almost entirely 
out of solution and a drop of the charge spotted out on a test 
filter paper will show almost no coloration in the seepage. The 
charge is delivered to a blow-case for pressure filtration. Dry- 
ing should be conducted at a low temperature, as for Amino 
Naphthol Red G. 


I22 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


The final volume of the charge should be that of about 15,000 
pounds of water; the reaction should be alkaline to the bicar- 
bonate stage and the temperature should not have risen above 10° 
C., before filtration is commenced. Only a slight excess of the 
component be shown when a drop of the charge is spotted on 
filter paper and the rim of the seepage tested with diazo benzene. 
Coupling takes place only slowly; a low temperature is neces- 
sary to hold the diazo from decomposition as long as possible 
and to cause precipitation of the dye on formation. With a 
diazo solution cooled to 5° C., and a large proportion of ice in 
coupling, the dye is almost completely precipitated and filters 
well, yielding a filter cake with 65 per cent moisture. Difficulty 
in obtaining the yield is met if the final volume is more than 
15,000 pounds for a molecule charge; salting is of little assist- 
ance for remedying a poorly controlled charge the character of 
the dye being such that salt added is not dissolved in the mother 
liquor but is included in the suspended dye, causing a low 
strength and dull shade in the product. If circumstances attend- 
ing the manufacture were such that Diazo-14 should be used in 
place of Diazo-13 for this preparation, the ease with which the 
volume and temperature could be controlled would be extremely 
favorable to the yield. 


The molecular weight of Amino Naphthol Red B is 566. The 
market wares of this dye are to be found greatly reduced, typical 
selling strengths being those which contain about 25 per cent of 
the pure dye and 75 per cent of salt; the occurrence of such a 
weakened standard may be attributed to the character of the 
factory product to be obtained with other than a systematized 
method of preparation. On the basis of the above mentioned 
reduction, a yield of 2,264 pounds of selling strength dye con- 
stitutes the yield theoretically possible from a molecule charge, 
and yields of over 2,000 pounds are met with in practice. At 
the prices prevailing in 1922 the total cost of materials consumed 
in a molecule charge may be stated at $460, which with a yield 
of 2,000 pounds and a manufaturing cost of 11 cents per pound 
brings the total cost of production to 34 cents per pound. The 
dye is applied to wool and silk in acid bath, the shade produced 


DIAZOTIZATION OF ACETYL PARA PHENYLENE DIAMINE 123 


being fast to light but less satisfactory toward washing treat- 
ments. Production of the dye in the United States during 1920 
amounted to 142,367 pounds, valued at $1.52 per pound. The 
price may be compared with the average selling price of $1.25 
per pound in 1921 and the market quotations of from 75 cents 
to $1.00 per pound in 1922. 


AZO CORALLINE* 


Prepared by coupling diazotized acetyl para phenylene diamine 
with “R” salt in alkaline solution. 


N,Cl 
\/\OH ie 
| ie ae 
NaSO, \40,SNa MOA 
NHCOCH, 
‘*R’? salt Diazo-13 
N= NS 
OH 
| | 
NasUs Zs 7 Oo Na Leh 
NHEOCH? 


Azo Coralline 


Preparation of the Dye.— 
Materials.— . 
355 lbs. “R” salt, 100 per cent 
2,000 lbs. water 


tub No. 3 
150 lbs. soda ash 
1,000 lbs. ice 
tub No. 8 
1 lb. mol. Diazo-13 
tub No. 5 


1,000 lbs. salt 


Method.—The location and dimensions of the tubs No. 3, 5 
and 8 are according to Plate F. 


22Azo Crimson L, Azo Grenadine Ll. 


I24 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Preparation of the component is made according to the direc- 
tions for its use in manufacture of Ponceau 2R, Chapter V, by 
dissolving 355 pounds of “R” salt, or one mol. plus 2 per cent 
excess, in 2,000 pounds of water in tub No. 3. The solution is 
allowed to cool by agitation until the following day, when it is 
delivered to tub No. 8 where 150 pounds of soda ash is added. 

Diazo-13 is prepared in tub No. 5. One thousand pounds of 
ice is entered in tub No. 8 with the component and the diazo is 
then delivered into tub No. 8 in as short a time as the frothing 
permits. Agitation is continued for four hours and the charge 
then tested to ascertain the completion of the coupling reaction. 
When a test shows the diazo to be completely utilized, steam is 
passed in to bring the temperature of the charge to 65° C., and 
precipitation then made by adding from 500 to 1,000 pounds of 
salt. The finished charge is delivered to a blow-case for pres- 
sure filtration. Drying should be conducted at a low temperature. 

The final volume of the charge is unimportant in this case as 
the dye is very little soluble under the conditions of its forma- 
tion. The dye precipitates in a form which filters poorly. Fil- 
tration is improved by heating to 65° C., to cause partial solution, 
and then precipitating with salt; heating to 85° C., gives still 
better filtration but if the high temperature is maintained long 
enough to bring about complete solution of the dye hydrolysis 
of the acetylamino group may set in, causing alteration in the 
shade of the product. An almost neutral condition is favorable 
to the filtration and lessens the possibility of decomposing the 
acetylamino group. At the best, a filter cake containing 70 per 
cent of moisture is obtained. “R” salt couplings filter poorly in 
general, varying somewhat with the grade of the intermediate 
used ; usually the dye precipitates in a fine, silty form and retards 
filtration by filling the interstices of the filter cloth; by employ- 
ing a pure grade of “R” salt, in the form of a Io per cent solu- 
tion filtered before use, the dye may be obtained in a more 
granular condition. “R” salt couplings usually precipitate com- 
pletely upon formation so that the filtration offers the chief 
difficulty in the production. 


DIAZOTIZATION OF ANTHRANILIC ACID 125 


Azo Coralline is used on wool and silk in acid bath to give 
a crimson shade. The molecular weight of the dye compound is 
509. As the selling strengths ordinarily contain about 30 per 
cent pure dye and 70 per cent salt, the yield of marketable dye 
theoretically possible from a molecule charge amounts to 1,696 
pounds and a factory yield of over 1,500 pounds is to be expected. 
The statistics of the domestic production are not available. 


Diazotization of Anthranilic Acid.?°— 
Anthranilic Acid, C,H,O,N, Molecular Weight = 137. 


NH N, — O 
By @ CO 


Anthranilic acid Diazo benzoic acid anhydride 


Materials.— 
137 lbs. anthranilic acid, 100 per cent = one mol. 
120 lbs. caustic soda solution, 40° Bé. 
72 \bs. nitrite of soda, technical 
1,000 lbs. water 


tub No. 3 
500 lbs. water 
250 Ibs. muriatic acid, 20° Be. 
1,000 lbs. ice 
tub No. 6 


Method.—A tub 6 feet in diameter and 6 feet deep, fitted with 
an agitator to turn at a speed of thirty revolutions per minute, 
such as tub No. 6, Plate F, is used for the diazotization. The 
amine is to be dissolved in a small tub such as No. 3, Plate F. 

One thousand pounds of water is entered in tub No. 3, filling 
to a depth of 10 inches. One hundred and thirty-seven pounds 
of anthranilic acid, 100 per cent, is added and dissolved by ad- 
dition of caustic soda solution in small excess; solution should 


29 Diazo-15. 


126 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


occur immediately without heating ; 72 pounds of technical nitrite 
of soda is then entered and dissolved with the amine. 

For diazotization, 500 pounds of water is entered in tub No. 
6 by filling to a depth of 3 inches. Two hundred and fifty 
pounds of muriatic acid, or two mols. plus 20 pounds, is added 
and followed by 500 pounds of ice. Agitation is commenced and 
the solution in tub No. 3 is delivered into the acid mixture in 
tub No. 6, taking thirty minutes for the addition; during diazoti- 
zation 500 pounds of ice is fed into tub No. 6. Diazotization is 
complete as soon as the solution in tub No. 3 has been discharged 
and the tub rinsed down. 

The diazo results in solution and, when prepared from a good 
grade of anthranilic acid, is almost white in color; small amounts 
of free nitrous acid and muriatic acid should be shown present 
by tests. Diazotization of anthranilic acid takes place rapidly 
and the diazo is fairly stable at ordinary temperatures; the 
temperature should not exceed 15° C., during diazotization, to 
avoid loss of nitrous acid through fuming. Preparation of the 
diazo by precipitating anthranilic acid in a finely divided state 
and leading in a solution of nitrite of soda gives results equally 
as satisfactory as the procedure outlined above; the method of 
dissolving the nitrite with the amine is practical and convenient, 
especially when the diazo results in solution. Another procedure, 
sometimes recommended, that of leading diluted acid into the 
cold alkaline solution of the amine and nitrite, is difficult to 
control; the acid must be entered very slowly and its handling 
is disagreeable; the sequence in which the chemical reactions 
take place in such a diazotization is not fixed but the conditions 
are very favorable to the formation of imino azo compounds. 


ACID ALIZARINE RED B” 


Prepared by coupling diazotized anthranilic acid with “R” salt 
in alkaline solution. 


80 Palatine Chrome Red B, Pigment Scarlet 3B. 


DIAZOTIZATION OF ANTHRANILIC ACID 127 


No ns ase ae 


eQ® OH COONa 
Baste ( 


NaSO, SO, tia NYY NaSO SO, RD 
**R”’ salt Diazo-15 Acid Alizarine Red B 


Preparation of the Dye.— 
Materials. — 
355 lbs. “R” salt, 100 per cent, in the form of a 10 per 
cent solution 
125 lbs. soda ash 
500 Ibs. ice 
; | tub No. 8 
1 lb. mol. Diazo-15 
tub No. 6 


Method.—A tub 9g feet in diameter and 6 feet deep, with an 
agitator to turn at a speed of thirty revolutions per minute, such 
as tub No. 8, Plate F, is used for the coupling. 

A quantity of a filtered stock solution of “R” salt containing 
355 pounds of the 100 per cent material, or one mol. plus 2 per 
cent excess, is entered in tub No. 8. For this purpose the exact 
percentage composition of the stock solution must be determined ; 
the solution is pumped from a storage tank, through a pipe termi- 
nating in a valve at the vicinity of the coupling tub, and measure- 
ment of the required quantity made by weighing in 100-pound 
lots. One hundred and twenty-five pounds of soda ash is entered 
with the “R” salt and allowed to dissolve while Diazo-15 is be- 
ing prepared in tub No. 6. 

When the diazo is prepared, the component is cooled by addi- 
tion of 500 pounds of ice and the diazo solution delivered into 
tub No. 8 in a stream adjusted so as to complete the addition in 
thirty minutes. Formation and precipitation of the dye follows 
immediately and as soon as the diazo has been added the charge 
may be tested to determine the completion of the coupling re- 
action and then delivered to a blow-case for pressure filtration. 
With an adequate air pressure filtration may be completed in 


128 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


from fifty to seventy hours, yielding four standard pressfuls of 
firm cake containing about 60 per cent of moisture. 


The final volume of the charge is that of about 8,000 pounds 
of water. Very little dye is dissolved in the mother liquor at 
this volume and no salt is required to complete the precipitation. 
An excellent yield is obtained, varying only with the quality of 
the intermediates employed. For selling purposes the dye is 
only moderately reduced; typical market wares are to be found 
with from 30 to 40 per cent of salt. The dye is applied to wool 
in acid bath and then subjected to an after-chroming treatment ; 
the shade produced is highly fast to light. Because of its light 
fastness and insolubility in oils or spirit solvents, the dye is a 
valuable coloring for pigments. Production of this dye in the 
United States during 1920 amounted to a total of 67,817 pounds 
valued at an average price of $1.99 per pound. 


CHAPTER IX 


MONO AZO DYES PREPARED FROM ORTHO AMINO PHENOL 
DERIVATIVES. CHROME BROWN R, PERI WOOL 
BLACK AND PALATINE CHROME VIOLET 


Diazotization of Nitro Amino Phenol 4: 2: 1.32— 
Nitro Amino Phenol, C,H,O,N,, Molecular Weight = 154. 


OH O-- 
DN N, 
rai | 
nse by 
NO, NO 
Nitro amino phenol Diazo oxide of nitro benzene 


Materials. — 
154 lbs. nitro amino phenol, 100 per cent = one mol. 
2,000 lbs. water 
1,000 lbs. ice 
130 lbs. muriatic acid, 20° Bé. 
tub No. 2 
72 |bs. nitrite of soda, technical 
300 Ibs. water 
special container 


Method.—A tub 5 feet in diameter and 5 feet deep, fitted with 
_ an agitator to turn at a speed of thirty-five revolutions per min- 
ute, such as tub No. 2, Plate F, is to be used for preparation of 
the amine and for the diazotization. A solution of 72 pounds 
of nitrite of soda in 300 pounds of water is prepared in a barrel 
located on the deck of tub No. 2; a bottom outlet in the barrel 
permits discharge of the nitrite solution into tub No. 2 during 
diazotization. 

To prepare the amine, 2,000 pounds of water is entered in 
tub No. 2 by filling to a depth of 20 inches; a quantity of nitro 
amino phenol containing 154 pounds of the Ioo per cent material 
is added and steam is then passed in to heat the mixture to 60° C. 


31 Diazo-16. 


130 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


The material should dissolve upon agitation for thirty minutes at 
this temperature and the solution is then allowed to cool to 40° C., 
under agitation. One thousand pounds of ice is added, where- 
upon the temperature drops to 15° C., or below, and most of 
the nitro amino phenol precipitates in a finely divided form. 
One hundred and thirty pounds of muriatic acid, or slightly over 
one mol., is now added; diazotization is then made by delivering 
the nitrite of soda solution onto the surface of the agitating 
mixture in tub No. 2, taking thirty minutes for the addition. 
The nitrite of soda should be easily taken up and diazotization 
completed within fifteen minutes after the nitrite has been added. 
The diazo results as a suspension of yellow crystal and should 
be tested for presence of muriatic and nitrous acids in slight 
excess. 

Diazotization of nitro amino phenol 4:2:1 offers little diff- 
culty. The diazo is stable and a lowered temperature is desirable 
only to prevent loss of nitrous acid by fuming; at 5° C., or be- 
low, the nitrite is only slowly taken up but at 12° to 15° the 
diazotization goes on rapidly. One molecule of muriatic acid 
can suffice for the diazotization and the occurrence of secondary 
reactions need not be anticipated. The diazo is only moderately 
reactive but couples with some components to form dyes which 
are used on wool, with after-chroming, to produce the darker 
shades, such as greens, browns and blacks. 


CHROME BROWN R 


Prepared by coupling diazotized nitro amino phenol with: meta 
phenylene diamine sulfonic acid in neutral solution. 


O-- NH, OH NH, 
¥: N, “a N=N 
© Bf Tr 
NH, NH, 
NO, SO,H NO, SO,Na 
Diazo-16 Phenylene diamine Chrome Brown R 


sulfonic acid 1:3:4 
Preparation of the Dye.— 
Phenylene Diamine Sulfonic Acid, C,H,O,N,S, 
Molecular Weight = 188. 


MONO AZO DYES FROM ORTHO AMINO PHENOL DERIVATIVES I31 


Materials.— 
192 lbs. phenylene diamine sulfonic acid, 100 per cent 
120 lbs. caustic soda solution, 40° Bé. 
1,500 lbs. water 
tub No. 3 
I Ib. mol. Diazo-16 
tub No. 2 


Method.—A tub 6 feet in diameter and 6 feet deep, such as 
No. 6, Plate F, fitted with an agitator to turn at a speed of forty 
revolutions per minute, is to be used for the coupling. The com- 
ponent is prepared in a tub such as No. 3, Plate F, and delivered 
to tub No. 6 for coupling. Filtration of the dye is made by 
vacuum, 


To prepare the component, 1,500 pounds of water is entered 
in tub No. 3 by filling to a depth of 15 inches; a quantity of 
meta phenylene diamine sulfonic acid containing 192 pounds of 
the 100 per cent material, or one mol. plus 2 per cent excess, is 
added and followed by sufficient caustic soda to neutralize the 
free acid; solution is obtained by agitating at 35° C., and any 
excess caustic soda present should be neutralized by addition of 
dilute acetic acid; the solution of the component is then deliv- 
ered to tub No. 6. 


Diazo-16 is to be prepared according to the directions previ- 
ously given; the final volume of the diazo suspenion should not 
be much greater than that of 3,500 pounds of water. Before 
coupling, the excess muriatic acid of the diazo is to be neutral- 
ized by addition of soda ash in small amounts but using no ex- 
cess. The diazo is then delivered into the solution of the com- 
ponent in tub No. 6 and allowed to couple until the following 
day, under agitation; the charge should then show absence of the 
diazo when a drop is spotted on filter paper and the rim of the 
seepage is tested with a drop of an alkaline beta naphthol solu- 
tion. The dye should be completely out of solution, in the form 
of dark brown particles; salting should be unnecessary with a 
final volume of about 5,000 pounds in the charge. The finished 
charge is delivered to a suction filter and filtered by vacuum. 


132 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


When prepared from pure intermediates, it shows no tendency 
to ignite and can be dried at the full heat of the ovens. 

During the above coupling the reaction should be maintained 
neutral. An alkaline condition is to be avoided as in such case 
the dye is held partly in solution and salting is necessary to ob- 
tain the full yield. A charge which has been coupled in the 
neutral condition should however be made slightly alkaline, with 
soda ash, previous to filtration; this treatment does not affect the 
yield and is advantageous to the filtration and the shade of the 
dye. 

The molecular weight of Chrome Brown R is 375; standard 
selling strength for the “Extra” brands usually is based upon a 
mixture of two parts pure dye and one part salt. The dye is 
applied to wool in acid bath with after-chroming, to produce deep 
shades of brown. 


PERI WOOL BLACK 


Prepared by coupling diazotized nitro amino phenol with 
peri phenyl naphthylamine sulfonic acid in neutral solution. 


O-,  (C,H,NHSO,Na 
N, N= N NHC,H, 
OE Oe 2 
i: Na 
NO, 


Diazo-16 Phenyl peri salt ate nine Black 


Preparation of the Dye.— 


Phenyl Peri Sodium Salt, C,,H,,O,NSNa, 
Molecular Weight = 321. 


Materials.— 
321 lbs. phenyl peri salt, 100 per cent in the fone of 6 per 
cent solution 
tub No. 6 
1 lb. mol. Diazo-16 
tub No. 2 


MONO AZO DYES FROM ORTHO AMINO PHENOL DERIVATIVES 133 


Method.—A tub 6 feet in diameter and 6 feet deep, such as 
tub No. 6, Plate F, fitted with an agitator to turn at a speed of 
forty revolutions per minute, is used for preparation of the com- 
ponent, and for the coupling; filtration of the dye is made by 
vacuum. 


Commercial phenyl naphthylamine sulfonic acid is obtained 
and used in the form of its solution, as isolation of this inter- 
mediate in the solid form is attended by too much difficulty to be 
practical. The technical solution produced generally contains 
from 10 to 15 per cent of the solid intermediate. For use in 
coupling a stock solution of phenyl naphthylamine sulfonic acid 
is to be stored in the azo building and as in the case of other 
stock solutions used similarly the required quantity is delivered 
to the vicinity of the coupling tub through a feed pipe and pump 
arrangement. 


Estimation of the true strength of a phenyl peri salt solution 
offers some difficulty. If an analysis is made by: titration with 
a standard solution of nitro diazo benzene, the figure obtained 
may represent impurities present as well as actual phenyl peri 
salt. The impurities do not couple with the weakly reactive diazo 
from nitro amino phenol, and can be discharged in filtration, 
leaving the dye uninjured, but in order to bring a proper pro- 
portion of phenyl peri salt into a coupling it is advisable to take 
an excess or at least 4 per cent over the amount shown by 
analysis. e 


To prepare the component a quantity of stock solution con- 
taining 321 pounds of the phenyl peri salt is weighed and, after 
entry in tub No. 6, is diluted to a strength of approximately 6 
per cent. Any alkalinity in the component due to presence of 
soda ash should be neutralized with dilute acetic acid, using 
Brilliant Yellow test paper as indicator. Coupling is to be made 
at ordinary temperature and in neutral condition. 

Diazo-16 is prepared in tub No. 2 according to the directions 
given and the excess muriatic acid present is neutralized with 
soda ash. ‘The diazo is then delivered into the component in 
tub No. 6, taking one hour for the addition. Agitation is con- 
tinued until the day following, when a test made by spotting a 


134 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


drop of the charge against an alkaline solution of beta naphthol 
should show absence of the diazo; a test for the presence of the 
component in excess is usually positive and of little significance. 
The dye should be practically all out of solution and no salting 
necessary. ‘The charge is made slightly alkaline with soda ash 
and then delivered to a suction filter tub; a practically quantita- 
tive yield is obtainable. When applied on wool with after-chrom- 
ing the dye produces a lustrous black. 


Diazotization of Amino Phenol Sulfonic Acid 2: 1: 4.3?— 
Amino Phenol Sulfonic Acid, C,H,O,NS, 
Molecular Weight = 189. 


OH O--5 


NH, N, 
Oy ae 


SO,H SO,Na 
Amino phenol Diazo oxide of benzene 
sulfonic acid 1:2:4 sodium sulfonate 
Materials.— 
189 lbs. amino phenol sulfonic acid, 100 per cent, = one 
mol. 


120 Ibs. caustic soda solution, 40° Bé. 
2,000 lbs. water 
72 lbs. nitrite of soda, technical 


tub No. 2 
150 Ibs. muriatic acid, 20° Bé. 
500 lbs. ice 
500 lbs. water 
tub No. 6 


Method.—A tub 6 feet in diameter and 6 feet deep, such as 
No. 6, Plate F, fitted with an agitator to turn at a speed of forty 
revolutions per minute, is used for the diazotization. The amine 
is prepared in a tub such as No. 2, Plate F. 

To dissolve the amine, 2,000 pounds of water is entered in tub 
No. 2, filling to a depth of 20 inches. One hundred and eighty- 


82 Diazo-17. 


MONO AZO DYES FROM ORTHO AMINO PHENOL DERIVATIVES 135 


nine pounds of ortho amino phenol para sulfonic acid 100 per 
cent, corresponding to one mol., is added and followed by 120 
pounds of caustic soda solution 40° Bé. density, or a quantity 
sufficient to make the mixture slightly alkaline to Brilliant 
Yellow paper. The mixture is agitated for a short time to effect 
solution and 72 pounds of technical nitrite of soda is then added 
and allowed to dissolve. 


For the diazotization, 500 pounds of water is entered in tub 
No. 6, filling to a depth of 3% inches, and followed by 500 
pounds of cracked ice and 150 pounds of muriatic acid 20° Bé. 
Agitation is commenced and the solution of the amine and nitrite 
in tub No. 2 is delivered into tub No. 6 in a stream adjusted so 
as to accupy thirty minutes for the addition. Diazotization 
should be complete within thirty minutes after the addition. The 
diazo results in solution with final volume equal to that of about 
3,500 pounds of water, and is stable towards most treatments. 
For coupling with beta naphthol the solution should be treated 
with sufficient soda ash to insure a neutral condition towards 
Congo Red test paper. 


PALATINE CHROME VIOLET 


Prepared by coupling diazotized amino phenol sulfonic acid 
with beta naphthol in alkaline solution. 


oes OH ez 
aa NaO/\/\ a ail 
eee a. oe 
va Wan Ve, 
,Na SO,Na Nae 
Diazo-17 Sodium beta Palatine Chrome Violet 


naphtholate 


Preparation of the Dye.— 
Materials.— 
147 lbs. beta naphthol, technical 
120 lbs. caustic soda solution, 40° Bé. 
1,000 Ibs. water 
tub No. 3 


136 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


1 lb. mol. Diazo-17 
| tub No. 6 
100 lbs. muriatic acid 
500 lbs. salt 


Method.—Tub No. 6 is to be used for the coupling. The com- 
ponent is prepared in a tub such as No. 3, Plate F. 

One thousand pounds of water is entered in tub No. 3, filling 
to a depth of 10 inches, and followed by 147 pounds of beta 
naphthol and 120 pounds of caustic soda solution 40° Bé. Solu- 
tion is obtained by heating to 65° C. and agitating at that tempera- 
ture for thirty minutes; the solution is allowed to cool until the 
following day. 

When the component is prepared, Diazo-17 is prepared in tub 
No. 6 according to directions given. The solution of the com- 
ponent is started flowing into tub No. 6, taking one hour for the 
addition. The coupling is allowed to agitate for three hours and 
the excess alkalinity is then destroyed by adding slowly 100 
pounds of muriatic acid. Agitation is continued until the follow- 
ing day, when the charge is salted out with 500 pounds of salt 
and delivered to a suction filter tub for filtration. - 


CHAPTER X 


MONO AZO DYES FROM ALPHA NAPHTHYLAMINE AND 


NAPHTHIONIC ACID 


Diazotization of Alpha Naphthylamine.*°— 
Alpha Naphthylamine, C,,H,N, Molecular Weight = 143. 


NH, N,Cl 


| ar | | 


Alpha naphthylamine Alpha diazo naphthalene chloride 


Materials.— 


143 lbs. 
150 lbs. 
4,000 lbs. 


150 lbs. 
250 lbs. 


4,500 lbs. 


75, Ibs. 
300 Ibs. 


alpha naphthylamine, 100 per cent, = one mol. 
muriatic acid, 20° Bé. 
water 

tub No. 3 
oil of vitriol, 66° Bé 
ice 

special container 

ice 

tub No. 5 
nitrite of soda, technical 
water 

tub No. 4 


Method.—For the diazotization, a tub 8 feet in diameter and 
6 feet deep, fitted with an agitator to turn at a speed of thirty 
revolutions per minute, such as tub No. 5, Plate F, is used. For 
dissolving the amine, a tub 5 feet in diameter and 5 feet deep, 
fitted with an agitator to turn at a speed of thirty revolutions 
per minute, such as tub No. 3, Plate F, located on the floor above 
tub No. 5, is used; the tub must be provided with a wooden 
steam pipe suitable for heating an acid mixture. The tub, No. 4, 
used for dissolving nitrite of soda should have a large outlet 
and a discharging pipe 2 inches in diameter for rapid delivery 
of the nitrite of soda solution during diazotization. A lead-lined 


33 Diazo-19. 


138 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


tub similar to that described for use in the manufacture of 
Metanile Yellow, is employed to contain a solution of sulfuric 
acid. In general the set of tubs used for preparing Diazo-19g is 
the same as for Diazo-7 and the set may be used alternately for 
each of these diazotizations. 


To prepare the amine, 4,000 pounds of water is entered in 
‘tub No. 3 by filling to a depth of 40 inches. One hundred and 
fifty pounds of muriatic acid, or 1.3 mols. is added and followed 
by 143 pounds of technically pure alpha naphthylamine. Steam 
is passed in to bring the temperature to 70° C., and the mixture 
is agitated at that temperature for thirty minutes. The naphthyl- 
amine at first melts and later solidifies partially as contact with 
the acid goes on; complete solution is obtained by continued heat- 
ing. The hot solution of alpha naphthylamine hydrochloride is 
delivered into tub No. 5 as rapidly as the large outlet of the tub 
permits and allowed to cool in tub No. 5 with agitation, until 
the temperature has dropped to between 47° C. and 45° C. 


A solution of sulfuric acid is prepared in the lead-lined tub 
above No. 5, from 250 pounds of cracked ice and 150 pounds oil 
of vitriol, and held in readiness. The cooling of the naphthyl- 
amine hydrochloride solution in tub No. 5 takes about thirty 
minutes and care must be taken that the temperature does not 
drop to the point where precipitation of the hydrochloride com- 
mences. When the desired temperature has been reached, the 
sulfuric acid solution is delivered rapidly into tub No. 5 and the 
naphthylamine precipitates completely in the form of its white, 
crystalline, sulfate. The suspension is allowed to cool to about 
30° C., by agitation. 

A solution of 75 pounds of technical nitrite of soda, or one 
mol. plus 3 pounds excess, is made in tub No. 4, using 300 pounds 
of water. For diazotization, the suspension of alpha naphthyl- 
amine sulfate in tub No. 5 is cooled to 0° C., by addition of 4,500 
pounds of cracked ice, and the nitrite of soda solution is then de- 
livered into the agitating mixture in tub No. 5 by opening the 
valve in the nitrite delivery pipe so as to perform the addition in 
one and one-half minutes. The nitrite should be immediately 
absorbed and no red fumes noticeable. The naphthylamine sul- 


MONO AZO DYES FROM ALPHA NAPHTHYLAMINE 139 


fate is quickly converted into the diazo and goes into solution. 
The diazo results as a strongly acid solution containing free 
nitrous acid in excess and, as the stability of the diazo is rela- 
tively low, its use in a coupling should be undertaken without 
delay. With the proportion of ice employed in the diazotization, 
the final temperature should not be much over 2° C., and the 
agitation may be halted finally as an aid in retaining the low 
temperature. 

The diazo solution should not have a greater volume than that 
of 10,000 pounds of water, filling the tub to a depth of 40 inches. 
Attempts to reduce the total volume by starting with less than 
4,000 pounds of water to dissolve the naphthylamine hydro- 
chloride are usually followed with unsatisfactory results. One- 
pound molecule of alpha naphthylamine hydrochloride can be 
readily dissolved in 4,000 pounds of water at 70° C.; with any 
appreciable reduction of this volume difficulty is met in obtain- 
ing complete solution, followed by an undesired reprecipitation 
of the hydrochloride on slight cooling, in a dense form which is 
diazotized only on prolonged agitation with nitrite, during which 
formation of the insoluble imino azo compound can take place. 
A successful diazotization is to be obtained by careful manipu- 
lation of the naphthylamine hydrochloride solution until precipi- 
tation of the sulfate has been effected, when, with a rapid distri- 
bution of the nitrite solution under good agitation, a minimum 
formation of the imino azo compound may be had and filtration 
of the diazo, a difficult operation sometimes recommended is un- 
necessary. At the low temperature required for diazotization 
and with the dilution obtained, a large proportion of the less 
active sulfuric acid is of advantage for promoting the speed of 
the reaction. 

The diazo from alpha naphthylamine exhibits a degree of re- 
activity for coupling somewhat less intense than that shown by 
diazo benzene but in general Diazo-19 can be coupled with beta 
naphthol, Schaeffer’s Salt and other salts by following procedures 
similar to those directed for the coupling of Diazo-1 with the 
various components. 


I40 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


FAST RED B* 


Prepared by coupling diazotized alpha naphthylamine with “R” 
salt in alkaline solution. 


ie Gee i /\ /\OH eo 
NaSO, \/ VO,SNa VV NaSO,\V/ VO,SNa VV 
eR Salt Diazo-19 Fast Red B 
Preparation of the Dye.— 
Materials.— 
355 lbs. “R” salt, 100 per cent, in the form of a Io per cent 
solution . 
250 lbs. soda ash 
1,000 lbs. ice 
tub No. 8 


I lb. mol. Diazo-19 
tub No. 5 
1,000 lbs. salt 


Method.—Coupling is made in a tub g feet in diameter and 6 
feet deep, such as tub No. 8, Plate F, fitted with an agitator to 
turn at a speed of thirty revolutions per minute and an iron 
steam pipe for heating the finished coupling prior to salting. 
Filtration is made by pressure and as the filtration of this dye is 
a difficult procedure, a good grade of “R” salt should be em- 
ployed, preferably in the form of a filtered 10 per cent stock 
solution. 

The necessary quantity of “R” salt solution is pumped from 
storage and, after analysis, is weighed into tub No. 8. Two 
hundred and fifty pounds of soda ash is entered and dissolved 
with the “R” salt solution, and Diazo-19 is then prepared in tub 
No. 5 as previously directed. 

For coupling, the component in tub No. 8 is cooled by addition 
of 1,000 pounds of ice and the diazo solution is delivered into 


34 Bordeaux B, etc., Cerasine R, Rouge B, Azo Bordeaux. 


MONO AZO DYES FROM ALPHA NAPHTHYLAMINE I4I 


tub No. 8 as rapidly as the frothing will perimit; the addition in 
such a case can go on rapidly at first, slowing up gradually as 
the soda ash is converted into bicarbonate, after which stage 
frothing may become dangerous. The addition can be completed 
within two hours and the coupling is then allowed to agitate 
until a test shows completion of the reaction. The dye pre- 
cipitates completely, but in a poor condition for filtering, and 
to obtain a form which will filter, steam is passed into the charge 
and heating carried on to bring the dye completely into solution, 
a temperature of 85° C. sufficing for the purpose. From 5 per 
cent to 10 per cent of salt on the weight of the charge is re- 
quired to precipitate the dye at this temperature; the salt should 
be added to the hot solution and dissolved completely so that the 
minimum amount may be used. When precipitation is completed, 
the charge is delivered to a blow-case, or better, divided between 
two blow-cases, and filtered. The charge cools down before 
filtration is even partly completed and filtration usually drags 
out for a number of days, especially if the diazotization of alpha 
naphthylamine has not been entirely successful; the yield to be 
obtained is in accordance with the success attained in diazotiza- 
tion. A large amount of salt is included in the precipitated dye, 
so that a reduced factory product is obtained and the strength 
of the standard to be adopted for selling purposes must be weak 
in proportion to permit further reduction in the mill room. 
Standard market wares ordinarily contain over 60 per cent of 
salt. | 


For difficult filtrations where the blow-case and press system 
is not well adapted, such as in the case of Fast Red B, a system 
of filtration on a revolving suction drum has been recommended, 
with advantages from removal of the dye as soon as filtered and 
the feasibility of holding the charge in the making tub at a 
high temperature until filtration is completed. By reducing the 
time of filtration and improving the character of the product, 
such a filtration system can afford much improvement in azo 
work in ‘cases where filtration offers the greatest difficulty in 
preparation of the dye. 


§ 


142 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Diazotization of Naphthionic Acid.*°— 
Sodium Naphthionate, C,,H,O,NSNa, 
Molecular Weight = 245. 


NH, Naame 
ae, Koy ee | 
WA , a ON 1 

eC | 

S0,H S08 
Naphthionic acid © Anhydride of diazo naphthalene 
sulfonic acid 


Materials. — 
490 lbs. sodium naphthionate, 100 per cent, = two mols. 
150 lbs. nitrite of soda, technical 
2,000 lbs. water 


tub No. 3 
500 Ibs. water 
805 lbs. muriatic acid, 20° Bé. 
2,000 lbs. ice 
tub No. 6 


Method.—For the diazotization, a tub 6 feet in diameter and 
6 feet deep, such as tub No. 6, Plate F, is used and should have 
an agitator to turn at a speed of forty revolutions per minute. A 
small tub such as No. 3, Plate F, is used for preparation of the 
amine. Previous to coupling, the diazo is to be filtered, by 
vacuum. 

For preparation of the amine, 2,000 pounds of water is entered 
in tub No. 3, filling to a depth of 20 inches; a quantity of sodium 
naphthionate, powder, equivalent to 490 pounds of the 100 per 
cent material, is added and dissolved by agitating for thirty min- 
utes. Solution is obtained without heating; 150 pounds of tech- 
nical nitrite of soda, an excess over two molecules, is then added 
and allowed to dissolve with the naphthionate. 

For the diazotization, 500 pounds of water is entered in tub 
No. 6, filling to a depth of about 3 inches, and 805 pounds of 
muriatic acid, equivalent to a total of seven molecules, is added 


85 Diazo-20, preparation of the diazo in charges of two-pound molecule size. 


MONO AZO DYES FROM NAPHTHIONIC ACID 143 


and followed with 500 pounds of cracked ice. Agitation is com- 
menced and the naphthionate-nitrite solution in tub No. 3 is 
started flowing into the acid mixture in tub No. 6 in a stream 
adjusted so as to occupy one hour for the addition; after the first 
twenty minutes has elapsed, and one-third of the naphthionate 
solution has been delivered, the addition is halted while 500 
pounds of ice is added to tub No. 6; the diazotization is then 
continued and another 500 pounds of ice is entered twenty min- 
utes later; when addition of the naphthionate has been completed, 
500 pounds of ice is entered and the agitation continued for an 
hour to complete the reaction. The diazo results in suspension 
as a fairly thick paste. A test is made to determine the complete- 
ness of the conversion of naphthionic acid to diazo and the charge 
then delivered to a suction filter located on the first floor; after 
filtration, the cake is washed twice from a shower arranged over 
the filter tub and finally pressed out with a hand float. The 
diazo meal is removed from the filter by means of a wooden 
shovel and placed in barrels for transfer to the tub where used, 
where it is mixed with 2,500 pounds of water to form a paste. 


The volume of the diazo suspension in the above two-molecule 
charge is about that of 6,000 pounds of water before the filtra- 
tion. At this volume the thickness of the paste obtained neces- 
sitates strong agitation, otherwise portions of an naphthionic acid 
remain undiazotized from lack of contact. If the agitation avail- 
able is less vigorous than that obtained at forty revolutions per 
minute, in a tub such as No. 6, greater dilution with ice is neces- 
sary, else the thickness of the paste retards the reaction and a 
considerable amount of nitrous acid may be lost through fuming. 
With suitable agitation, a temperature of 10° C., is desirable to 
prevent loss of nitrous acid during the diazotization. Theoretic- 
ally only two molecules of muriatic acid should be required for 
the chemistry of diazotization of sodium naphthionate, as in the 
case of sodium sulfanilate, but for sodium naphthionate a larger 
proportion of acid, up to three and one-half mols., is generally 
employed to prevent occurrence of secondary reaction between 


144. FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


the diazo and undiazotized naphthionic acid. The completion of 
diazotization is recognized by treating a 20 cc. sample of the 
charge in a beaker with 4o cc. of water and making the mixture 
alkaline with a Io per cent solution of sodium carbonate; the 
yellow color of the diazo may deepen but should not become red, 
as would be the case if undiazotized naphthionate were present 
to react with the diazo. 


The procedure of dissolving sodium nitrite with the amine 
and leading the solution into an acid mixture is the most suitable 
method for diazotizing naphthionic acid when a small final 
volume is desired. As the first portions of the naphthionate- 
nitrite solution enter the acid mixture, good distribution is ob- 
tained and a fairly rapid diazotization becomes possible; as the 
proportion of naphthionate increases, dilution with ice and the 
agitation described is sufficient to overcome the caking that occurs 
when naphthionic acid is precipitated in small volume. If the 
diazotization were to be conducted by first precipitating the 
naphthionic acid in tub No. 6 and then leading in a solution of 
sodium nitrate, the smallest volume at which the precipitation 
could be made to give a paste sufficiently thin to allow reaction 
with the nitrite would be 8,o00 pounds for the two-molecule 
charge; the final volume in such case would not be less than that 
of 10,000 pounds of water and the time required for diazotization 
would extend up to five hours. 


FAST BROWN N 


Prepared by coupling diazotized naphthionic acid with alpha 
naphthol in alkaline solution. 


OH pee HO YN=N SO,Na 
PC « 
ONS ue WR NE” 
| 
80-4 


Alpha naphthol = Diazo-20 Fast Brown N 


MONO AZO DYES FROM NAPHTHIONIC ACID 145 


Preparation of the Dye.— 


Maiterials.— 
288 lbs. alph naphthol, refined, = two mols. 
240 lbs. caustic soda solution, 40° Bé. 
25 lbs. soda ash 
1,400 lbs. water 


tub No. 2 
1,000 lbs. ice 
tub No. 6 
2 lb. mol. Diazo-20 
2,500 lbs. water 
tub No. 3 


1,000 Ibs. salt 


Method.—For preparation of this dye, tubs with the locations 
and dimensions of No. 2, 3 and 6, Plate F, are to be used. Coup- 
ling is made in tub No. 6 and the filtration made by vacuum. 


To prepare the component, 1,400 pounds of water is entered 
in tub No. 2, filling to a depth of 14 inches. Two hundred and 
eighty-eight pounds of alpha naphthol, or two mols., is added and 
followed by 240 pounds of caustic soda solution of 40° Bé. 
density and 25 pounds of soda ash. Solution is made by heat- 
ing to 60° C., and maintaining the temperature for thirty minutes. 
The solution is then allowed to cool under agitation. 


The preparation of Diazo-20 commenced simultaneously with 
_ that of the component, and the diazo, after filtration, is entered 
in tub No. 3 with 2,500 pounds of water. The partially cooled 
solution of the component is delivered into tub No. 6 and the 
temperature brought below 15° C., by addition of 1,000 pounds 
of cracked ice. The diazo suspension in tub No. 3 is then deliv- 
ered into tub No. 6, taking one hour for the addition. The re- 
action of the coupling mixture should remain alkaline, and very 
little frothing should occur. Agitation of the charge is continued 
until a test shows the presence of either diazo or component 
in excess. Precipitation of the dye is then completed by gradu- 
ally adding salt until a spotting test is satisfactory and the charge 
then delivered to a suction filter tub on the first floor. 


146 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


By use of the proportion stated above a slight excess of alpha 
naphthol should be present in the finished charge, as some diazo 
is lost in the filtration and transfer to tub No. 3. Excess of the 
component has less objectionable influence on the dye than an 
excess of the diazo. The dye is applied to wool in acid bath, 
producing a brown orange shade. Statistics as to production in 
1920 are not available. 


FAST RED A* 


Prepared by coupling diazotized naphthionic acid with beta 
naphthol in alkaline solution. 


N.-7 N sseeeeaa ay 
A AOH AVEO RS \ OEY ia 
NE teh pire bid lysate od ok ba 
VV Vie VV VV 
| so,- SO,Na 
Beta naphthol Diazo-20 Fast Red A 
Preparation of the Dye.— 
Materials.— 
294 lbs. beta naphthol, technical 
240 lbs. caustic soda solution, 40° Bé. 
25 lbs. soda ash 
1,500 lbs. water 
tub No. 2 
1,000 Ibs. ice 
2 lb. mol. Diazo-20 
2,500 lbs. water 
tub No. 3 


1,000 lbs. salt 


Preparation of this dye follows the same course as that of 
Fast Brown N and a slight excess of the component should be 
present in the finished charge. 


38 Rocelline. 


MONO AZO DYES FROM NAPHTHIONIC ACID 147 


AZO RUBIN* 


Prepared by coupling diazotized naphthionic acid with the 1:4 
naphthol sulfonic or Nevile-Winther acid, in alkaline solution. 


OH N.--7 OH 
/\/\ ihe | AWN N= oo>SO,Na 
Pere ee ieObe, veriagels liv] sia da 
VV eee VV 
SO,H So,- SO,Na 
Nevile- Diazo-20 Azo Rubin 


Winther acid 


Preparation of the Dye.— 
Nevile-Winther Acid, C,,H,O,S, Molecular Weight = 224. 
Materials.— 
457 lbs. Nevile-Winther acid, 100 per cent 
240 lbs. caustic soda solution, 40° Bé. 
3,000 lbs. water 
200 lbs. soda ash 


tub No. 2 
2 lbs. mol. Diazo-20 
2,500 lbs. water 
tub No. 6 
1,500 lbs. ice 
1,500 lbs. salt 
tub No. 8 


Method.—Coupling is made in a tub such as No. 8, Plate F, 
and the dye is filtered by pressure. 

To prepare the component, 457 pounds of Nevile-Winther acid, 
100 per cent, corresponding to two molecules plus 2 per cent ex- 
cess, is entered in tub No. 2 with 3,000 pounds of water and 
neutralized with caustic soda solution. Steam is passed in and 
solution made by heating at 4o° C. for thirty minutes; 200 
pounds of soda ash is then added in tub No. 2 and completely 
dissolved. The solution is delivered to tub No. 8, on the first 
floor, and allowed to cool under agitation while Diazo-20 is being 
prepared i in tub No. 6. 


37 Carmoisine, Azo Acid Fuchsine, Fast Red C, Brilliant Crimson. 


148 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


For this coupling the filtered diazo is returned to tub No. 6 
and mixed to a paste with 2,500 pounds of water. The tempera- 
ture of the component in tub No. 8 is brought below 15° C., by 
addition of 1,500 pounds of ice and the diazo suspension in tub 
No. 6 is then delivered into tub No. 8, taking thirty minutes for 
the addition. The coupling is agitated until the following day 
and precipitation is then completed by addition of 1,500 pounds 
of salt. The charge is delivered to a blow-case for pressure fil- 
tration. 

The final volume of the charge should not be greater than that 
of 7,000 pounds of water. A small volume is favorable to an 
easy and complete precipitation of the dye with less than 1,500 
pounds of salt, whereby an almost quantitative yield is obtained. 
Filtration of the dye is a slow operation, proceeding at a rate 
slightly better than that of the average R salt combination; with 
a well restricted volume, filtration may be completed with one 
filter press in about fifty hours. The employment of a filtered 
diazo is not imperative for this coupling but with an unfiltered 
diazo the final volume of a two-molecule charge cannot be held 
under 10,000 pounds, whereby the difficulty of completely pre- 
cipitating the dye is increased and the time required by filtration 
extends up to one hundred hours, so that advantages from use 
of a filtered diazo compensate the extra work. 

The molecular weight of Azo Rubin is 502. As selling strengths 
ordinarily contain about 40 per cent pure dye and 60 per cent of 
salt, 2,510 pounds of market ware constitutes the yield theoretic- 
ally possible from a two-molecule charge. Production of the 
dye in the United States during 1920 totaled 470,949 pounds, 
valued at $1.43 per pound. 


CHAPTER XI 


MONO AZO DYES PREPARED FROM AMINO NAPHTHOL SUL- 
FONIC ACIDS. SALICINE BLACK U AND SULFON 
ACID BLUE R 


Diazotization of Amino Naphthol Sulfonic Acid, 1: 2: 4.38— 
1:2:4 Acid, C,,H,O,NS, Molecular Weight = 2309. 


NH, N.-7 
)" 
=> 
\ 
SO,H SO,Na 
P20 4 Acid Diazo oxide of naphthalene 
sodium sulfonate 
Materials.— 
1,195 lbs. 1:2:4 acid, 100 per cent, = five mols. 
200 lbs. salt 


15 lbs. blue vitriol 
3,000 lbs. water 
1,500 lbs. ice 
tub No. 5 
365 lbs. nitrite of soda, technical 
750 lbs. water 
tub No. I 
3 Ibs. bisulfite of soda 


Method.—A tub 8 feet in diameter and 6 feet deep, fitted with 
an agitator to turn at a speed of thirty revolutions per minute, 
such as tub No. 5, Plate F, is used for the diazotization. To pre- 
pare the nitrite of soda solution, 750 pounds of water is entered 
in the small tub No. 1, Plate F, filling to a depth of 20 inches; 
the water is heated to 85° C., and 365 pounds of technical nitrite 
of soda, or five mols, plus 5 pounds excess, is added and dissolved 
by stirring with a paddle; the solution will have cooled to room 
temperature at the time of diazotization. 


88 Diazo-21, preparation of the diazo in five-pound molecule quantity. 


150 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Commercial amino naphthol sulfonic acid, 1:2:4, is obtain- 
able in a high degree of purity, and is handled as a powder con- 
taining over 92 per cent of the pure material, or as a 40 per cent 
paste. 

For the diazotization, a quantity of the intermediate equal to 
I,195 pounds of the 100 per cent material, either in paste or 
powder form, is entered in tub No. 5; water is then run in to a 
depth of 16 inches, to make a total of 3,000 pounds of water. 
The mixture is agitated until well mixed, and further prepared 
by addition of 200 pounds of salt and a solution of 15 pounds 
of blue vitriol dissolved in hot water. ‘The suspension is to be 
exactly neutralized to Congo Red test paper by addition of diluted 
caustic soda solution. ‘The temperature is then brought below 
15° C. by addition of 500 pounds of cracked ice, and the nitrite of 
soda solution is started flowing slowly onto the surface of the sus- 
pension in tub No. 5. ‘The flow of the nitrite solution is adjusted 
so as to occupy two hours; diazotization goes on slowly and 
entry of the nitrite solution must be controlled in accordance with 
the consumption of the nitrous acid liberated. Additional ice, 
up to 1,000 pounds, is required during diazotization to maintain 
a temperature below 15° C. Agitation is continued for an hour 
after the nitrite has been added, when a sample of the diazo 
should dissolve completely upon dilution with water, and a por- 
tion acidulated with pure dilute hydrochloric acid should show 
presence of a slight excess of nitrous acid when tested with starch 
potassium iodide paper. Diazotization may then be considered 
complete and the excess nitrous acid destroyed by addition of a 
dilute, acidified solution of bisulfite of soda. The diazo results 
as a suspension of bronze crystals, and when once formed, is 
stable toward most treatments. | 

Under the conditions outlined above the diazotization may be 
expected to proceed smoothly and without irregularities. By a 
hurried introduction of the nitrite, or with inadequate agitation, 
nitrous acid may accumulate faster than it is consumed in diazo- ° 
tization; under such conditions the 1:2:4 acid may undergo 
oxidation, indicated by evolution of red fumes and a partial 


MONO AZO DYES FROM AMINO NAPHTHOL SULFONIC ACIDS I5I 


blackening of the charge; inefficient agitation is frequently ac- 
companied by such irregularity. 


SALICINE BLACK U*® 
Prepared by coupling diazotized amino naphthol sulfonic acid 
I:2:4 with beta naphthol in alkaline solution and precipitating 
the dye in neutral solution. 


Be oo OF ca 


pia Beta naphthol ae Bice U 
Preparation of the Dye.— 
Materials.— 


735 lbs. beta naphthol, technical 
600 lbs. caustic soda solution, 40° Bé. 
4,000 Ibs. water 


tub No. 3 
5 lb. mols. Diazo-21 
1,000 Ibs. ice 
tub No. 5 
500 lbs. muriatic acid, 20° Bé 
500 lbs. water 
tub No. 2 


_ Method.—The location and dimensions of tubs No. 2, 3 and 
5, used in this preparation, are according to Plate F.. Coupling 
and precipitation of the dye is conducted in tub No. 5. Filtration 
is made by vacuum using a filter tub located on the first floor. 

In preparation of the component, 4,000 pounds of water is 
entered in tub No. 3, filling to a depth of 4o inches; 735 pounds 
of beta naphthol is added and followed by 600 pounds of caustic 
soda solution of 40° Bé. density. The solution obtained by 
agitating at 70° C. for thirty minutes is allowed to stand over 
night to cool to ordinary temperature. 


39 Palatine Chrome Black 6B, Eriochrome Blue Black R, Acid Alizarine Black A, 
Diamond Blue Black EB, Anthracene Blue Black BE. Preparation of the dye in 
charges of five-molecule size. 


II 


152 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Coupling: Diazo-21 is prepared in tub No. 5 according to 
directions given; the finished diazo is cooled to 5° C. by addition 
of 1,000 pounds of cracked ice. The solution of the component 
in tub No. 3 is then delivered into tub No. 5, under the surface 
of the diazo suspension. ‘The time taken for the addition should 
be extended through two hours; a too rapid entry of the naphthol 
frequently causes uncontrollable foaming. The coupling is agi- 
tated over night and on the following day is found as a dark 
blue solution. To precipitate the dye, 500 pounds of muriatic 
acid, or less than five mols., is diluted with an equal volume of 
water in tub No. 2, and the acid delivered very slowly into the 
coupling in tub No. 5, to exactly neutralize the alkalinity of the 
charge; during this treatment the dye precipitates completely. 
Excess acid over the amount required for neutralization is un- 
desirable and addition of the final portion should be made care- 
fully; it is preferable to leave reaction neutral than faintly acid 
to Congo Red test paper. The charge is delivered to a suction 
filter tub for filtration in portions, the filtration usually proceed- 
ing rapidly. Drying is best conducted at a temperature of 75° 
C. or below. 

The molecular weight of Salicine Black U is 416. A common 
standard for selling strength is that containing one part pure dye 
and one part salt; on the basis of such reduction the yield of 
marketable dye theoretically possible from a five-molecule charge 
amounts to about 4,160 pounds; yields of over 3,500 pounds are 
ordinarily had in practice. The dye is a highly important chrome 
color, for wool, production in the United States during 1920 
amounting to 1,074,248 pounds, valued at $1.10 per pound. 

The preparation of Erio Chrome Blue Black B is similar to 
that of Salicine Black U, alpha naphthol replacing beta naphthol 
as component ; the coupling for Erio Chrome Blue Black B offers 
greater difficulty and is advisably conducted in charges of not 
over two-molecule size. 


Diazotization of “H” Acid.4°— 
“H” Acid Disodium Salt, C,,H,O,NS,Na, 
Molecular Weight = 363. 


4 Diazo-22. 


MONO AZO DYES FROM AMINO NAPHTHOL SULFONIC ACIDS 153 


NH, OH N,—O 
a. te AG 5 
SONNE STONOIN 50,0 
““H”’ acid disodium salt Diazo oxide of naphthalene 
. disulfonic acid 
Materials.— 
341 Ibs. ““H” acid disodium salt, 100 per cent, = one mol. 


115 lbs. caustic soda solution, 40° Bé. 
75 lbs. nitrite of soda, technical 
Soo lbs. water 


tub No. 2 
250 lbs. muriatic acid, 20° Bé. 
1,000 lbs. water 
1,500 Ibs, ice 
tub No. 6 


Method.—A tub 6 feet in diameter and 6 feet deep, fitted with 
an agitator to turn at a speed of forty revolutions per minute, 
such as tub No. 6, Plate F, is used for the diazotization. 

The amine is prepared in a tub such as No. 2, Plate F, by enter- 
ing 800 pounds of water and a quantity of the intermediate cor- 
responding to 341 pounds of the 100 per cent material, based on 
the molecular weight of the monosodium salt. As the commercial 
product is usually acid in composition, it must be neutralized 
with sufficient caustic soda solution to faintly redden a Brilliant 
Yellow test paper. Solution is obtained by agitating for thirty - 
minutes, and 75 pounds of technical nitrite of soda, or one 
mol. plus 5 per cent excess, is then added and dissolved with the 
Ci acic. 

For diazotization, 1,000 pounds of water is entered in tub No. 
6; 250 pounds of muriatic acid, or two mols. plus 20 pounds ex- 
cess, is added and followed by 500 pounds of cracked ice. The 
solution of “H” acid in tub No. 2 is then delivered slowly onto 
the surface of the agitating mixture in tub No. 6; two hours’ 
time should be allowed for the addition; the desirable tempera- 
ture is between 10° and 15° C., and the temperature is main- 
tained by addition of up to 1,000 pounds of ice. Diazotization 


154 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


goes on rapidly; the diazo forms as a bright yellow crystalline 
suspension; the difficulty of diazotization arises chiefly from the 
heaviness of the paste which is formed. Contact between the 
reacting materials may be improved by diluting the mixture with 
ice and water but in general strong agitation gives satisfactory 
results without increasing the volume. With agitation such as 
that obtained in tub No. 6 at forty revolutions per minute, and 
addition of the “H” acid solution in a fine stream, the operation 
may be completed within three hours’ time; a test portion of the 
diazo should then be completely soluble upon dilution with water ; 
the diazo is usually slightly acid to Congo Red paper and contains 
excess free nitrous acid. 

Diazotized “H” acid shows little tendency to decompose under 
the conditions obtained in the above method. A very low tem- 
perature is undesirable; under 2° C., diazotization proceeds 
slowly and fuming of nitrous acid occurs, while the undiazotized 
particles form granules which offer resistance to diazotization 
when the temperature finally rises. A certain amount of such 
granulation, or clotting, is to be met with by too hurried addition 
of the “H” acid solution. 


SULFON ACID BLUE R 


Prepared by coupling diazotized “H” acid with peri phenyl 
naphthylamine sulfonic acid in neutral solution. 


Preparation of the Dye.— 


C.H,NH SO,Na N,—O 
hike, naso\ A A, 
Pheny] peri salt Diazo-22 SO,Na 


Sulfon Acid BlueR ~%0sNa 


MONO AZO DYES FROM AMINO NAPHTHOL SULFONIC ACIDS 155 


Materials.— 
321 Ibs. phenyl peri salt, 100 per cent 
in the form of a solution 
100 lbs. bicarbonate of soda 
tub No. 8 
1 lb. mol. Diazo-22 
tub No. 6 


Method.—Coupling is made in a tub such as No. 8, Plate F. 
The dye is filtered by pressure. 


As in the preparation of Peri Wool Black, Chapter IX, the 
phenyl peri acid must be used in the form of a solution. A 
quantity of stock solution of the intermediate, containing 321 
pounds of the 100 per cent material based on the molecular 
weight of the sodium salt, is entered in tub No. 8 and diluted with 
sufficient ice and water to bring the concentration to approx- 
imately 6 per cent of phenyl peri salt and the temperature to 
12° C. Before coupling 100 pounds of bicarbonate of soda is 
added and dissolved in the solution of the component. 

Diazo-22 is prepared according to the directions given and de- 
livered ino the component in tub No. 8, taking two hours for the 
addition. The phenyl peri acid is easily thrown out of solution 
and addition of the diazo must be made slowly to allow neutrali- 
zation upon contact with the component. The coupling reaction 
proceeds quickly when no irregularity develops but a charge is 
customarily agitated over night for completion and on the day 
following is made slightly alkaline by addition of soda ash and 
then delivered to a blow-case for pressure filtration. 

The final volume of the charge should not be much greater 
than that of 10,000 pounds of water. The volume has important 
influence as the yield begins to drop off rapidly when the final 
volume of a molecule charge becomes greater than the figure 
above. A small amount of salt will precipitate the dye com- 
pletely from an abnormally large volume but in such case the 
shade and bloom of the product is injured. Filtration should 
proceed rapidly; poor filtration quality in a charge may be at- 
tributed to presence of phenyl peri acid precipitated during 


156 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


coupling, as the precipitated material is not easily redissolved and 
has a gummy character. In general, the phenyl peri salt requires 
coupling in a fairly well diluted condition and at a temperature 
of 10° C. or above; to maintain neutrality during coupling, bi- 
carbonate of soda is preferable to the acetate; when the acetate is 
employed for coupling with an acid diazo the acetic acid formed 
must be neutralized by running in a solution of bicarbonate dur- 
ing addition of the diazo, or precipitation of the phenyl peri acid 
occurs; under good agitation, the frothing which results from 
neutralization with bicarbonate does not offer immoderate dif- 
ficulty in control. 


The molecular weight of Sulfon Acid Blue R is 695. The dye 
is reduced, by milling with sodium sulfate, to a selling strength 
which ordinarily corresponds to a mixture of one part pure dye 
and one part sodium sulfate, so that the yield theoretically pos- 
sible from a one-molecule charge amounts to about 1,690 pounds 
of market ware. Reduction is made with sodium sulfate to 
facilitate application of the dye in a bath weakly acidified with 
acetic acid; a fine blue shade is produced on wool. Ordinarily 
the yield may be held to a high average, the chief disadvantage 
to manufacture of the dye lying in the high cost of the phenyl 
peri salt. Production of the dye in the United States during 
1920 amounted to 454,185 pounds, valued at $1.95 per pound. 


CHAPTER XII 


TETRAZOTIZATION OF BENZIDINE AND PREPARATION OF 
DIAMOND FLAVINE G, CHRYSAMINE G AND 
DIAMINE FAST RED C 


Tetrazotization of Benzidine.— 
Benzidine, C,,H,,.N,, Molecular Weight = 184, 


NH, N,Cl 
9 ) 
as aS ts 
WV Sy 
NH, N,Cl 
Benzidine Tetrazo diphenyl dichloride 


Materials.— 
184 lbs. benzidine base, 100 per cent, = one mol. 
250 lbs. muriatic acid, 20° Bé. 
2,000 lbs. water 


tub No. 2 
230 lbs. muriatic acid, 20° Bé. 
- 1,500 lbs. ice 
tub No. 6 
144 lbs. nitrite of soda, technical 
400 lbs. water 
tub No. 4 


3 lbs. bisulfite of soda 


Method.—The tetrazotization is to be conducted in a tub 6 
feet in diameter and 6 feet deep, equipped with an agitator to 
turn at a speed of forty revolutions per minute, such as tub No. 
6, Plate F. The diamine is first dissolved, on an upper floor, in 
a smaller tub, such as No. 2, Plate F. 

For holding the nitrite of soda solution, a small tub such as 
No. 4 is to be used; this tub must be equipped with the large 


158 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


outlet and delivery pipe, of 14-inch size, described in the diazo- 
tization of the nitranilines and alpha naphthylamine, for very 
rapid discharge of the nitrite solution during the tetrazotization. 
To prepare the nitrite solution, 400 pounds of water is entered in 
tub No. 4 and heated to 70° C.; 144 pounds of technical nitrite of 
soda, or two mols., is added and dissolved by stirring with a 
paddle; the solution is held in readiness. 


To prepare the diamine, 2,000 pounds of water is entered in 
tub No. 2, filling to a depth of 20 inches, and followed by 250 
pounds of muriatic acid. A quantity of benzidine base, either 
the paste or the dry form, containing 184 pounds of the 100 per 
cent material, is added; steam is passed in and the mixture is 
agitated at 75° C., for thirty minutes, at the end of which time 
a clear solution of benzidine hydrochloride should be obtained. 

This solution is delivered without delay to tub No. 6, and tub 
No. 2 should be rinsed down; after agitation for two hours in 
tub No. 6 the temperature will have dropped to about 40° C., at 
which point crystallization of the hydrochloride begins. The 
mixture is now cooled to 5° C., by addition of up to 1,500 pounds 
of ice, whereupon further precipitation of the hydrochloride 
takes place; 230 pounds of muriatic acid is now added, making 
a total of over four mols. present for the tetrazotization. 

Tetrazotization is made by opening the valve in the nitrite de- 
livery pipe leading from tub No. 4, so as to discharge the nitrite 
solution onto the surface of the agitating mixture in tub No. 6 
in a stream which occupies about one and one-half minutes for 
completion. The nitrite should be rapidly taken up and no 
fuming should occur; the tetrazotization is considered complete 
within fifteen minutes after addition of the nitrite and the solu- 
tion of the tetrazo should be acid to Congo Red test paper and 
show presence of nitrous acid in excess. The excess nitrous 
acid should be destroyed by gradually adding small amounts of 
a 10 per cent solution of sodium bisulfite until a starch potassium 
iodide paper is left white when treated with a drop of the tetrazo. 

The final volume of the solution should be that of about 5,000 
pounds of water, filling the tub to a depth of 33 inches; the tem- 
perature rises to about 12° C. When a pure quality of benzidine 


\ 
TETRAZOTIZATION OF BENZIDINE 159 


is available tetrazotization can proceed smoothly in the presence 
of slightly over four molecules of muriatic acid, as with the pure 
material there is little tendency to form secondary compounds; 
when an impure benzidine is used, the impurities very often give 
rise to secondary compounds and a good tetrazotization is then 
made only in the presence of from five to six molecules of muri- 
atic acid. In the case when very low grades of benzidine are used, 
it is best to dissolve the one-molecule quantity of benzidine in a 
greater amount of water than 2,000 pounds and then filter the 
solution of the hydrochloride previous to tetrazotizing. 


DIAMOND FLAVINE G 


Prepared by coupling tetrazotized benzidine with one molecule 
of salicylic acid in alkaline solution with filtration of the coupling 
in acid condition and subsequently converting the unattacked 
diazonium group into hydroxyl. 


N,Cl OH NeaNeg > 30H Ne=N <2 0H 
- ae \ COONa \ COONa 
| | 
Vis Gear ry a: ne 
ras Sodium /\ /\ 
| | salicylate | | cet 
V/ \V/ Ws 
N,Cl N,Cl OH 

Tetrazotized Intermediate Diamond 

benzidine compound Flavine G 


Preparation of the Dye.— 


Materials.— 

138 lbs. salicylic acid, technically pure 

115 lbs. caustic soda solution, 40° Bé. 

700 lbs. water 

150 lbs. soda ash 
tub No. 3 

1 lb. mol. tetrazotized benzidine 
1,000 Ibs. ice 

tub No. 6 


160 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


300 Ibs. muriatic acid 
1,500 lbs. ice 
250 lbs. oil of vitriol, 66° Bé. 


tub No. 2 
1,350 lbs. water 
150 lbs. vitriol 
tub No. 5 
6,000 lbs. water 
120 lbs. caustic soda solution, 40° Bé. 
25 lbs. soda ash 
1,000 lbs. salt 
tub No. 6 


Method.—The work of coupling is to be conducted in tub No. 
6, Plate F, subsequent to the tetrazotization of benzidine in this 
tub. The solution of sodium salicylate used as component is 
prepared in a tub such as No. 3, Plate F, on the upper floor; a 
large tub, 8 feet in diameter and 6 feet deep, located on the 
second floor, is employed for conversion of the diazonium group, 
and should be provided with a wooden steam pipe for heating 
an acid mixture. Three filtration operations are required two 
of which are in the acid condition; for the first acid filtration, 
a wool-covered suction filter tub is employed, and for the second, 
using pressure, a lead-lined blow-case and wooden plate filter 
press. 

To prepare the component, 700 pounds of water is entered in 
tub No. 3, filling to a depth of 7 inches; 138 pounds of tech- 
nically pure salicylic acid is entered and dissolved by addition of 
115 pounds of caustic soda solution of 40° Bé. density. No ex- 
cess Salicylic acid is desired and the amount directed is intended 
to furnish one pound molecule as closely as possible, without ex- 
cess. Solution is made by agitating for thirty minutes in the cold, 
and 150 pounds of soda ash is then added and allowed to dissolve 
completely by agitation. 

For the coupling, 184 pounds of benzidine is to be tetrazotized 
in tub No. 6 according to the directions given. Preparation of 
the tetrazo and component should be undertaken simultaneously. 


TETRAZOTIZATION OF BENZIDINE 161 


The excess muriatic acid of the tetrazo is first neutralized by ad- 
dition of 10 pounds of soda ash, and the temperature is then 
brought to 5° C. by addition of 500 pounds of cracked ice. ‘The 
alkaline solution of salicylic acid in tub No. 3 is now delivered 
into the tetrazo in tub No. 6, taking thirty minutes for the addi- 
ion. The coupling reaction should be complete within 3 hours’ 
time; the temperature is maintained at 5° C. throughout, by ad- 
dition of further ice.** 

First Filtration: The finished coupling is acidified to test with 
Congo Red paper, by entering slowly sufficient muriatic acid ;*? 
the acid form of the coupling precipitates completely, and the 
charge is delivered to a suction filter tub and, after filtration, is 
thoroughly pressed out. The cake is removed from the filter 
bed, using a wooden shovel, and entered in barrels for transfer 
to tub No. 2 on the third floor; here it is entered in an acid mix- 
ture made from 1,500 pounds of ice and 250 pounds of oil of 
vitriol, and mixed to an even paste after adding sufficient water 
to bring the total volume to 3,000 pounds, or a depth of 30 inches 
in tub No. 2. 

Conversion: A solution of sulfuric acid is made in tub No. 5 
by slowly entering 150 pounds of vitriol in 1,350 pounds of water; 
the heat of solution is utilized, and steam is also passed in to 
bring the temperature to 85° C. The acid suspension in tub No. 
2 is then started flowing into the hot acid mixture in tub No. 5 
and a temperature of 85° C. is maintained in tub No. 5 through- 
out the addition, which should be completed in two hours; heat- 
ing is continued until no further evolution of nitrogen is given, 
and no test for the diazonium group is shown by spotting a drop 
of the charge and testing with an alkaline beta naphthol solution. 
The charge is then allowed to cool under agitation, and finally 
delivered to a blow-case and filtered. Filtration is slow and takes 
a number of hours. Most of the acid is then washed out of the 
cake by running water through the press. 

For completion of the charge, 6,000 pounds of water is entered 
in tub No. 6, filling to a depth of 40 inches. The filtered charge 


41 At this point, the charge may be carried on for preparation of Chrysamine G, 
as taken up later. 
42 See preparation of Diamine Fast Red C. 


162 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


is entered and stirred to an even paste. A solution of 120 pounds 
of caustic soda, 40° Bé., diluted in tub No. 3 with 250 pounds of 
water, is delivered slowly into tub No. 6, to neutralize the charge 
partially, and sufficient soda ash is then added in tub No. 6 to 
complete the neutralization and create a slightly alkaline condi- 
tion. Steam is then passed in to bring the temperature to 85° C. 
and the temperature maintained until the dye goes completely 
into solution; the hot solution is then salted out by addition of 
about 1,000 pounds of salt, and the hot charge is delivered to a 
cotton-covered suction filter tub and pressed out as much as pos- 
sible after filtration. Drying and milling are conducted as for 
other dyes. 


CHRYSAMINE G 


Prepared by coupling tetrazotized benzidine with two molecules 
of salicylic acid in alkaline solution. 


NGl OH N=N< >OH: Ne=Neee 

/\ 2 COONa é COONa ‘ COONa 

led | 

V Li San Sarees sig OH V 

Fay Sodium /\ ACOONaS fe 

| | Salicylate ha | | = | | 

V V V V Hiss 

N,Cl N,Cl N=N<_ >OH 
Tetrazotized Intermediate COONa 

benzidine compound Chrysamine G 


Preparation of the Dye.— 
Materials.— 
For the first coupling, see preparation of Diamond Flavine G. 
150 lbs. salicylic acid, technical 
120 lbs. caustic soda solution 40° Bé. 
700 lbs. water 7 
tub No. 3 
120 lbs. caustic soda solution 40° Bé. 
250 lbs. water 
tub No. 4 


TETRAZOTIZATION OF BENZIDINE 163 


Method.—The dye is to be prepared in a tub such as No. 6, 
Plate F, and filtration is to be made by pressure. The first 
coupling, of tetrazotized benzidine and one molecule of salicylic 
acid, is to be conducted according to the directions given for 
preparation of Diamond Flavine G, up to the point indicated for 
Chrysamine G. 

For the second coupling, a solution of 150 pounds of tech- 
nically pure salicylic acid in 700 pounds of water and 120 pounds 
of caustic soda solution, 40° Bé. density, is prepared in tub No. 
3, and a solution of 120 pounds of caustic soda, 40° Bé. in 250 
pounds of water is made up in tub No. 4. 

When the first coupling has been completed in tub No. 6, the 
second molecule of sodium salicylate is delivered from tub No. 
3 into tub No. 6. Steam is passed in to warm the charge to 30° 
C., and the solution of caustic soda in tub No. 4 is delivered 
slowly into the charge, taking two hours for its addition. The 
charge is then delivered into tub No. 8 and allowed to agitate over 
night. On the following day the dye should be found completely 
out of solution, and the charge then delivered to a blow-case for 
pressure filtration. 


DIAMINE FAST RED C 


Prepared by coupling tetrazotized benzidine with one molecule 
of salicylic acid in alkaline solution, followed by coupling with 
the 2:8:6 amino naphthol sulfonic acid, or “Gamma Acid,” in a 
weakly acid solution. 


NN. OF 
1s ANNE ES 
| 
SO,Na 


Diamine Fast Red C 


164 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Preparation of the Dye.— 


Gamma Acid, C,,H,O,NS, Molecular Weight = 2309. 
Materials.— 
For the first coupling, see preparation of Diamond Flavine G. 
250 lbs. gamma acid, 100 per cent 
120 lbs. caustic soda solution 40° Bé. 
2,500 Ibs. water 


tub No. 3 
130 lbs. muriatic acid, 20° Bé. 
250 lbs. acetate of soda crystals 
300 lbs. soda ash 
1,000 Ibs. water 
tub No. 8 


1,000 Ibs. salt 


Method.—The dye is to be prepared in a tub such as No. 6, 
Plate F, and filtration is to be made by pressure. The first 
coupling, of tetrazotized benzidine and one molecule of salicylic 
acid, is to be conducted according to the directions given for the 
preparation of Diamond Flavine G, up to the point indicated for 
the Diamine Fast Red C. 

In preparation of the component for the second coupling, 
2,500 pounds of water is entered in tub No. 3, filling to a depth 
of 25 inches, and followed by a quantity of gamma acid con- 
taining 250 pounds of the 100 per cent material, or one mol. plus 
4 per cent excess; solution is obtained by agitating for thirty 
minutes with sufficient caustic soda solution to give an alkaline 
reaction; the gamma acid is then reprecipitated in a fine state of 
division by adding sufficient muriatic acid, about 130 pounds of 
20° Bé. acid sufficing. The excess muriatic acid is then neu- 
tralized by addition of acetate of soda, the final condition of the 
component being that of a weakly acetic acid suspension. 

The first coupling for this dye, as prepared under the heading 
of Diamond Flavine G, consists of an acid condition of the diazo- 
benzidine-azo-salicylic compound in tub No. 6; 250 pounds of 
acetate of soda crystals are added to the first coupling and the 


TETRAZOTIZATION OF BENZIDINE 165 


suspension of the component held in tub No. 3 is then delivered 
into tub No. 6 and the charge is agitated over night. 


To complete the charge in the alkaline condition, a solution of 
300 pounds of soda ash in 1,000 pounds of water is prepared in 
tub No. 3 and delivered into tub No. 8 and the charge in tub 
No. 6 is delivered into tub No. 8; the addition must be made 
slowly to avoid frothing over. The charge should be definitely 
alkaline in reaction. Salt is added, up to 1,000 pounds, to com- 
pletely precipitate the dye and the charge is delivered to a blow- 
case for pressure filtration. 


CHAPTER XIII 


RELATION OF THE CHEMIST TO THE INDUSTRY. EXPERI- 
MENTAL WORK AND SMALL SCALE PRODUCTION 


In the manufacture of dyes and intermediates the number of 
professionally trained employees required to carry on the work 
forms a high percentage of the total help, as a result of the techni- 
cal and varied character of the work. The circumstance has 
been dwelt upon, in the educational advertising campaigns of 
dye manufacturers, that as a matter of experience rather than 
point of view a minimum ratio of one professionally trained 
chemist to ten operators is compatible with successful produc- 
tion. The chemistry of a factory process allows the possibility 
of varied results, similar to a laboratory experiment. While for 
the azo dyes the mechanical features of a process, such as the 
filtration, drying and milling, may be regulated and conducted in 
the factory by non-professional operators, the chemical nature 
of the “making” operation resists standardization to the extent 
that every factory charge is in degree an experiment whose 
course must be followed by a chemist as for a laboratory ex- 
periment. 


If any one dye were to be produced continually in amount it 
would seem practical to train operators for the routine process 
adopted and dispense with most of the personal control by the 
chemist. Standardization of processes in this manner is more 
prevalent in the manufacture of synthetic drugs, perfumes and 
toilet goods, where the output consists of a limited number of 
standard products put up in small package for retail consumption. 
In such industries the chemical production involves a relatively 
smaller percentage of the total employed, as one kettle or still 
or mixer furnishes sufficient stock daily to give employment to 
many persons in the work of finishing, that is, bottling, pack- 
ing and distributing. The chemical operations conducted are 
fully as technical as those of the dye industry, but the identity of 
the articles produced is seldom varied and constant repetition 
gives the process a mechanical rather than chemical character. 


RELATION OF THE CHEMIST TO THE INDUSTRY 167 


The dye industry, especially in the case of azo dyes, is re- 
quired to manufacture a large number of products. ‘The dyes 
are numerous and the demand for each type fluctuates. To 
stock a full line of the different types is possible for only the 
largest firms. Packing and distribution is of smaller importance 
as the dye is usually put up in bulk, for industrial consumption. 
The work devolves practically on preparing the dye from valu- 
able raw materials whose properties can be estimated with diffi- 
culty by even the chemist. 


The chemical personnel finds occupation both in the laboratory 
and the factory. The factory chemist works as or with a fore- 
man to carry out processes similar to those described in the 
previous chapters. In the laboratory chemists are required for 
analysis and experimental work. The necessity for maintaining 
an analytical laboratory with at least one professionally trained 
chemist devoting full time to analysis is seldom questioned, but 
the extent to which a research or experimental department is de- 
veloped varies with the status of each concern. Some manufac- 
turers maintain a research department as a training school for 
factory chemists while others require the factory chemist to de- 
vote part time to the experimental work. Nevertheless the value 
of such industrial research is steadily becoming better known; 
it is a question chiefly of an investment to show returns by 
finding the way to more economical production and the develop- 
ment of new and better types of dye. 


An organized system for small scale experimentation on pro- 
cesses is very desirable when the adoption of new and untried 
methods is considered or when alterations are to be made for 
improvement of methods in use. Without such a system it is 
difficult to obtain exact information for properly working a 
method under the conditions of any one factory, and to proceed 
to manufacturing from written directions too often results in 
great waste to be permissible as a general procedure. The 
practicability of a new method, or idea, cannot be fully demon- 
strated by means of test experiments conducted in the ordinary 
chemical laboratory. The technique of such laboratory work 
involves experimentation with very small quantities of material, 

12 


168 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


usually on the 1/1oth-gram molecule scale, in glass or porcelain 
vessels cooled by an ice bath or heated with an open flame; ex- 
cellent filtration facilities are had with the Buchner suction funnel 
and the small amount of dye can be dried within twenty-four 
hours. The laboratory work is done by the chemist and derives all 
advantage possible from his observation and care and it is then 
possible to obtain excellent results with complex methods and 
difficult conditions. In the factory the work must be done with 
unskilled operators and, with the matter of profit imperative, 
the method which appears successful in the laboratory may 
often as not fall short of satisfaction, notwithstanding the super- 
vision by a chemist. Laboratory investigation is necessary and 
valuable as the first step in estimating the value of a process but 
the information afforded cannot be applied directly to factory 
routine charges for experimentation on a large scale. 


Experimentation must be considered from a more purely 
scientific standpoint than that held for production. It is some- 
times necessary to investigate conditions which are influencing 
a method adversely and in such cases while the information de- 
rived is valuable, it is obvious that the product of a charge con- 
ducted for such a purpose is of little value for selling purposes. 
In order to obtain data satisfactorily, after a method has been 
investigated on the 1/10th-gram molecule scale in the laboratory 
it must be possible to conduct experimentation on the smallest 
scale that simulates actual factory conditions. For this purpose 
a set of small-sized equipment should be available; installation 
of such equipment can be justified by the advantages obtained 
from its use in stabilizing factory procedure and by its use in 
production of small quantities of dyes less commonly required, 
for sale or use in shading of standard products. For the azo 
dyes, a suitable scale for experimental factory work is that which 
allows conducting of charges as small as the 1/1oth-pound mole- 
cule size, in small wooden tubs patterned after those used in 
ordinary factory work; cooling must be made by addition of ice 
and heating by steam passed directly into the charge as in the 
factory; filtration is most suitably made by vacuum in a small 
filter tub. Plate H illustrates the construction and arrangement 


RELATION OF THE CHEMIST TO THE INDUSTRY 169 









searee 


as re Plot foria 






t= i —— 




















"bdr TL Ope tele Wa : 
vata : 40 


ELEVATION” 1929222 


PLATE a 


170 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


of three tubs and a suction filter, for use in an experimental out- 
fit to conform with the requirements of charges as small as 
1/1oth-pound molecule. The tubs are advisably constructed 
from 2-inch stock, tub A to be 2 feet in diameter and 2 feet deep, 
tub B 3 feet by 3 feet and tub C 4 feet by 4 feet, with agitators 
in B and C to turn at a speed of forty revolutions per minute, 
and in A at thirty revolutions per minute. For heating materials 
in the largest tub, C, where most of the couplings of the experi- 
mentation are made, a permanent wooden steam pipe should be in- 
stalled similar to the use in the factory; for tubs A and B a removy- 
able brass or lead pipe with steam connection will serve; fixed 
water connections to the tubs are unnecessary as water can be 
entered by means of a small hose. Ice is to be carried up to the 
tubs in buckets. For diazotization of small charges, nitrite of 
soda may be dissolved in a bucket and delivered under the sur- 
face of the charge through a large wooden funnel held by hand; 
for some charges the diazotization may be conducted in tub C 
and tub A used for dissolving the nitrite. Transfer of contents 
between tubs is made through a 3-inch rubber hose. The filter 
tub is elevated from the floor to allow access with buckets at the 
bottom outlet when it is desired to recover a filtrate, and the 
location of the filter tub is made with a view to allowing the 
contents of any of the tubs to be discharged into it through a 
large hose. 

With care in operation, a single set of three tubs and filter 
such as described above will permit preparation of almost any 
azo dye in; a maaner; which sreproduces.the essentials of a large 
scale: factory process; ut due to’ the- ‘difficult 4y Gf washing out 
the colors completely one set of tubs should be available for the 
dark colors and: another set for the. light colors. Practical points 
to be observed in the éxperimental work include approximation 
of the time required to bring about solution of materials, com- 
pletion of reactions, the sequence to be followed in transferring 
mixtures between tubs, the efficacy of the agitation and the ex- 
tent to which volumes increase. It is not necessary that the 
plan of the experimental outfit be carried out to an extent which 


RELATION OF THE CHEMIST TO THE INDUSTRY I7I 


duplicates each detail of factory equipment; for the more ex- 
tended work, such as that of the disazo and trisazo dyes, with 
only three tubs available it may be necessary to use one tub for 
several stages of the charge, in which case the contents of a 
lower tub may be transferred to an upper by means of buckets, to 
leave the lower tub free for the next step. 


The quantity of material which can be produced in an experi- 
mental outfit of the size described will vary from 50 to 250 
pounds of standard ware. Operation cost on the amount pre- 
pared is often high enough to overcome profit and for actual 
production purposes the set is best used in the cases of the higher 
priced dyes which are less conveniently prepared in the larger 
tubs of the factory. A dye such as Orange I could be prepared 
in one-half molecule quantity in the small set more satisfactorily 
than on the molecule scale recommended for the factory pro- 
duction. 

The following outline may be used to illustrate the general 
course taken in experimental work. The preparation of Helian- 
thin, or Orange III, is given in Chapter VIII, based on the 
principle of dissolving the component, or dimethyl aniline, in the 
excess acid of the diazo, diazo benzene sulfonate, the coupling 
reaction being completed by neutralization. An alternative 
method, of Moehlau and Bucherer,** is as follows: 

Twenty-one grams of sulfanilic acid is mixed with 12 grams 
of dimethyl aniline and 100 cc. of water; a clear solution should 
-result; 6.9 grams of sodium nitrite dissolved in 50 cc. of water 
is added; gradually the mixture becomes yellow and deposits 
gold yellow crystals of Helianthin. The yield is almost quanti- 
tative. 

An explanation of the chemistry of the reaction involved in 
this method may be based upon the hydrolysis of the salt of 
dimethyl aniline and sulfanilic acid. The sulfanilic acid re- 
generated reacts with sodium nitrite to form nitrous acid and 
diazotization ensues, followed progressively by coupling of the 
diazo and dimethyl aniline. 


438 Farbenchemisches Praktikum, (1908), 135. 


172 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


NH, NH, 


5-020 


SO,H N(CH,), SO, — N(CH,), 


N= 
fo 

+ NaNO,=> | | | =| +2H,0 
i ee 


In so far as is apparent from its statement the method offers 
features of excellence, including the great desiderata of sim- 
plicity in operation and favorable yield. Cost of material con- 
sumed is at a minimum as only those chemicals are used which 
of themselves form a part of the product and no icing or salt 
is necessary. The employment of such a method should be con- 
sidered when it is desired to manufacture Helianthin. 


The directions given form sufficient basis for a laboratory ex- 
periment on the 1/10-gram molecule scale, using 6.9 grams of 
pure sodium nitrite. The 21-gram quantity of sulfanilic acid 
directed may be considered as referring to the pure crystalline 
material with two molecules of water of crystallization and a 
molecular weight of 207; in an experiment conducted for com- 
mercial purposes this quantity would need to be adjusted pro- 
portionately for employment of the commercial sulfanilic acid 
with a molecular weight of 173, and in general the commercial 
grades of materials must be employed if the results of the ex- 
periment are to have value for manufacturing. 

Laboratory experiments conducted with a view to demonstrat- 
ing the adaptability of this method should evolve information on 
the following points: the feasibility of dissolving 1/10-gram 
molecule quantities of sulfanilic acid and dimethyl aniline in the 
100 cc. quantity of water; the manner suitable for introducing 
the nitrite of soda, whether the solid material may be added 
directly to the reaction mixture or whether a solution of the 
nitrite may be added rapidly or allowed to flow in slowly; the in- 


RELATION OF THE CHEMIST TO THE INDUSTRY 1735 


fluence of the volume and agitation and the range of temperature 
during the reaction; the completeness of precipitation of the dye 
without salting. It would also be desirable to note whether the 
nitrous acid formed for diazotization had effect upon the dimethyl 
aniline present. Several laboratory tests may be conducted 
simultaneously and from the results of these first hand evidence 
as to the practicability of the chemical features of the method 
may be had quickly and at small cost. From the data obtained 
by laboratory experimentation proportions for a small trial 
charge may be calculated, and in this instance the experimental 
plant described earlier in the chapter affords equipment for con- 
ducting charges of any fraction of a pound molecule size. 


The following outlines, Methyl Red and Butter Yellow, are 
given to illustrate use of the experimental set in small scale pro- 
duction. 


METHYL RED 


Prepared by coupling diazotized anthranilic acid with dimethyl 
aniline. 


Materials.—For one-fourth-pound molecule charge. 
35 lbs. anthranilic acid, 100 per cent 
30 Ibs. caustic soda solution, 40° Bé. 
19 Ibs. nitrite of soda, technical 
250 Ibs. water 


tub B 
150 lbs. water 
250 lbs. ice 
100 Ibs. muriatic acid, 20° Bé. 
| tub C 
| 70 lbs. acetate of soda crystals 
150 lbs. water 
tub A 


2 lbs. bisulfite of soda 
' 20 lbs. dimethyl aniline 


174 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


Method.—The diazotization of anthranilic acid for this prepa- 
ration follows the method outlined in Chapter VIII in connection 
with the preparation of Acid Alizarine Red B. 


Two hundred and fifty pounds of water is entered in tub B, 
filling to a depth of 7 inches; 35 pounds of pure anthranilic acid 
is added and followed by 30 pounds of caustic soda solution 
40° Bé. density. Solution of the amine is obtained by agitating 
for fifteen minutes and 19 pounds of technical nitrite of soda 
is then added and allowed to dissolve with the amine. 


For the diazotization a cooling, acid, mixture is prepared in 
tub C by entering water to a depth of 2% inches, followed by 
250 pounds of ice and 100 pounds of muriatic acid 20° Bé. 
density. Agitation is commenced in tub C as soon as the mix- 
ture melts sufficiently and the sodium anthranilate-nitrite solu- 
tion in tub B is then delivered into tub C through a 3-inch hose, 
taking thirty minutes for the addition. Diazotization should be 
complete as soon as the addition has been made; the diazo re- 
sults in solution; the excess nitrous acid present should be de- 
stroyed by carefully adding portions of a Io per cent sodium 
bisulfite solution until no further test for nitrous acid is shown; 
this treatment is necessary to prevent formation of nitroso 
dimethyl aniline in small amounts. 


When the diazo has been prepared, 30 pounds of dimethyl an- 
iline, corresponding to slightly less than one-fourth-pound mol- 
ecule, is entered in tub C and allowed to dissolve with the diazo; 
the mixture is to be agitated for thirty minutes. A solution of ace- 
tate of soda, previously prepared by entering water to a depth of 
10 inches in tub A and dissolving 70 pounds of the crystalline 
acetate, is delivered into tub C in a stream adjusted so as to 
occupy two hours for the addition; the dye gradually precipitates 
as a bluish red material. The charge is allowed to agitate over 
night and on the following day excess diazo should be shown 
present by the spotting test; no odor of dimethyl aniline should 
be noticeable. The final volume is about that of 1,000 pounds 
of water, filling the tub to a depth of 17 inches. The charge 
filters well and the yield obtainable with the method is practically 
quantitative. To obtain a pure grade product, for use as indi- 


RELATION OF THE CHEMIST TO THE INDUSTRY 175 


cator, the dye is not dried, but after filtering and pressing out 
thoroughly is purified on a laboratory scale by recrystallizing 
from six parts of glacial acetic acid and finally drying at ordinary 
temperature. 


BUTTER YELLOW 


Prepared by coupling diazotized aniline with dimethyl] aniline. 
Materials.—For one-half-pound molecule charge. 
47 lbs. aniline oil 
180 lbs. muriatic acid, 20° Bé. 
1,000 lbs. ice 


tub C 
37 lbs. nitrite of soda, technical 
150 lbs. water 
tub A 
150 Ibs. acetate of soda 
300 Ibs. water 
tub B 


2 Ibs. bisulfite of soda 
60 lbs. dimethyl aniline 


Method.—The diazotization of aniline for this preparation 
follows the method outline in Chapter ITI. 


A nitrite of soda solution is prepared in tub A, by entering 
150 pounds of water, filling to a depth of Io inches, and dis- 
solving 37 pounds of technical nitrite of soda. Five hundred 
pounds of cracked ice is then entered in tub C and followed by 
180 pounds of muriatic acid 20° density and 47 pounds of 
aniline oil; a small amount of water is added to loosen the mix- 
ture and the agitator is then carefully started. The nitrite of 
soda solution is then delivered onto the surface of the agitating 
mixture in tub C, taking thirty minutes for the addition and 
holding the temperature below 2° C., by addition of 500 pounds 
of ice. Diazotization is finished and tested according to the 
directions given in the method of Chapter III, and the excess 
nitrous acid is to be destroyed by adding sufficient 10 per cent 
bisulfite of soda solution. 


176 FACTORY PRACTICE IN MANUFACTURE OF AZO DYES 


When the diazotization has been completed, 60 pounds of 
dimethyl aniline, or slightly less than one-half-pound molecule, is 
entered in tub C and allowed to dissolve in the excess acid of the 
diazo. The solution is agitated for thirty minutes. A solution 
of acetate of soda, previously prepared in tub B by entering 
300 pounds of water, filling to a depth of 8 inches, and dissolv- 
ing 150 pounds of the crystalline acetate, is now delivered into 
the coupling in tub C, taking two hours for the addition. The 
mixture is allowed to agitate over night and the dye precipitates 
completely. The final volume of the charge is about that of 
1,750 pounds of water, filling the tub to a depth of 27 inches. 
The crude product may be purified by recrystallization from 
ten parts of alcohol, and dried at a low temperature. — 


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